Flat tube, flat tube heat exchanger, and method of manufacturing same

ABSTRACT

A number of flat tubes, flat tube heat exchangers, and methods of manufacturing both are described and illustrated. The flat tubes can be constructed of one, two, or more pieces of sheet material. A profiled insert integral with the flat tube or constructed from another sheet of material can be used to define multiple flow channels through the flat tube. The flat tubes can be constructed of relatively thin material, and can be reinforced with folds of the flat tube material and/or of an insert in areas subject to higher pressure and thermal stresses. Also, the relatively thin flat tube material can have a corrosion layer enabling the material to resist failure due to corrosion. Heat exchangers having such flat tubes connected to collection tubes are also disclosed, as are manners in which such tubes can be provided with fins.

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority is hereby claimed to German Patent Application No. DE 10 2006 002 627.6, filed Jan. 19, 2006, and to German Patent Application No. DE 10 2006 002 789.2, filed on Jan. 20, 2006, and to German Patent Application No. DE 10 2006 002 932.1, filed on Jan. 21, 2006, and to German Patent Application No. DE 10 2006 006 670.7, filed Feb. 14, 2006, and to German Patent Application No. DE 10 2006 016 711.2, filed Apr. 8, 2006, and to German Patent Application No. DE 10 2006 029 378.9, filed Jun. 27, 2006, and to German Patent Application No. DE 10 2006 032 406.4, filed Jul. 13, 2006, and to German Patent Application No. DE 10 2006 033 568.6, filed Jul. 20, 2006, and to German Patent Application No. DE 10 2006 035 210.6, filed Jul. 29, 2006, and to German Patent Application No. DE 10 2006 041 270.2, filed Sep. 2, 2006, and to German Patent Application No. DE 10 2006 042 427.1, filed Sep. 9, 2006, the entire contents of which are incorporated herein by reference.

SUMMARY

In some embodiments, the present invention provides a heat exchanger tube including a tube body at least partially defined by a sheet of material having a thickness of no greater than about 0.15 mm, the tube body having a thickness, a width larger than and substantially perpendicular to the thickness, an outer wall defined at least in part by the sheet of material, an internal chamber having a maximum width extending in a direction of the width of the tube body, a broad side, and first and second narrow sides each defining an interior surface of the internal chamber, the sheet of material being bent to at least partially define the first narrow side of the tube body. The heat exchanger of the present invention can also include a first portion of the outer wall overlapping a second portion of the outer wall at the second narrow end and defining a seam, wherein the first portion has an end at a location along the width of the tube, and wherein the internal chamber extends from a center of the tube past the location to the interior surface of the second narrow side.

The present invention also provides a heat exchanger tube including a sheet of material at least partially forming an outer wall of a tube body having a first narrow side, a second narrow side, and a broad side, the sheet of material having a thickness of less than about 0.15 mm and being folded at the first narrow side of the tube body, the first narrow side and the second narrow side being reinforced such that each of the first narrow side and the second narrow side have a thickness greater than the thickness of the sheet of material.

In addition, the present invention provides method of forming a heat exchanger tube including the act of shaping a sheet of material having a thickness of less than about 0.15 mm to form a tube body having a thickness, a width larger than and substantially perpendicular to the thickness, an outer wall defined at least in part by the sheet of material, an internal chamber having a maximum width extending in a direction of the width of the tube body, a broad side, and first and second narrow sides each defining an interior surface of the internal chamber. The method can also include the acts of bending the sheet of material to at least partially define the first narrow side of the tube body, and overlapping a first portion of the outer wall with a second portion of the outer wall at the second narrow end and forming a seam, the first portion of the outer wall having an end at a location along the width of the tube, and the internal chamber extending from a center of the tube past the location to the interior surface of the second narrow side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a tube according to some embodiments of the present invention.

FIG. 2 is an enlarged view of an end of the tube shown in FIG. 1.

FIG. 3 schematically illustrates a set of exemplary manufacturing steps that can be used to form the tube shown in FIG. 1.

FIG. 4 is an enlarged view of a narrow side of the tube shown in FIG. 1.

FIG. 5 is another enlarged view of the narrow side shown in FIG. 1.

FIG. 6 is an enlarged view of a narrow side of a tube according to another embodiment of the present invention.

FIG. 7 is an enlarged view of a narrow side of a tube according to yet another embodiment of the present invention.

FIG. 8 is an enlarged view of a narrow side of a tube according to still another embodiment of the present invention.

FIG. 9 is an enlarged view of a narrow side of a tube according to another embodiment of the present invention.

FIG. 10 is an enlarged view of a narrow side of a tube according to yet another embodiment of the present invention.

FIG. 11 a narrow side of a tube according to still another embodiment of the present invention.

FIG. 12 is an enlarged view of a portion of a tube including internal folds according another embodiment of the present invention.

FIG. 13 is an enlarged view of a portion of a tube including internal folds according to yet another embodiment of the present invention.

FIG. 14 is an enlarged view of a portion of a tube including an insert according to still another embodiment of the present invention.

FIG. 15 is an enlarged view of a portion of a tube including an insert according to another embodiment of the present invention.

FIG. 16 schematically illustrates a set of exemplary manufacturing steps that can be used to form a tube including first and second portions formed from a common piece of folded material.

FIG. 17 is an enlarged view of a tube including first and second portions formed from a common piece of folded material according to still another embodiment of the present invention.

FIG. 18 is an enlarged view of a tube including first and second portions formed from a common piece of folded material according to another embodiment of the present invention.

FIG. 19 is a side view of a tube including first and second portions formed from a common piece of folded material according to yet another embodiment of the present invention.

FIG. 20 is a side view of a tube including first and second portions formed from a common piece of folded material according to still another embodiment of the present invention.

FIG. 21 is a side view of a tube including first and second portions formed from a common piece of folded material according to another embodiment of the present invention.

FIG. 22 is a side view of a tube including first and second portions formed from a common piece of folded material according to yet another embodiment of the present invention.

FIG. 23 is a side view of a tube including first and second portions formed from a common piece of folded material according to still another embodiment of the present invention.

FIG. 24 is an enlarged view of a tube including first and second portions formed from a common piece of folded material according to another embodiment of the present invention.

FIG. 25 is an exploded view of a tube including first and second portions and an insert positioned between the first and second portions according to some embodiments of the present invention.

FIG. 26 is an exploded view of the tube shown in FIG. 25.

FIG. 27 is an exploded view of a tube including first and second portions and an insert positioned between the first and second portions according to still another embodiment of the present invention.

FIG. 28 is a side view of the tube including first and second portions and an insert positioned between the first and second portions according to yet another embodiment of the present invention.

FIG. 29 is an enlarged view of a portion of the tube shown in FIG. 28.

FIG. 30 is a side view of a tube including first and second portions and an insert positioned between the first and second portions according to still another embodiment of the present invention.

FIG. 31 is an enlarged view of a portion of the tube shown in FIG. 30.

FIG. 32A is a side view of a tube including first and second portions and an insert positioned between the first and second portions according to yet another embodiment of the present invention.

FIG. 32B is an enlarged view of a portion of the tube shown in FIG. 32A.

FIG. 33 is a side view of a portion of a tube including first and second portions and an insert positioned between the first and second portions according to another embodiment of the present invention.

FIG. 34 illustrates ten embodiments of tubes according to some embodiments of the present invention.

FIG. 35 is a side view of a tube according to some embodiments of the present invention.

FIG. 36 is a side view of an internal insert for the tube shown in FIG. 35.

FIG. 37 is a top view of the internal insert shown in FIG. 36.

FIG. 38 is a perspective view of a portion of the internal insert shown in FIG. 35.

FIG. 39 is a side view of a tube according to some embodiments of the present invention.

FIG. 40 is an enlarged perspective view of an internal insert for the tube shown in FIG. 39.

FIG. 41 is a perspective view of a portion of the internal insert shown in FIG. 40.

FIG. 42 is an enlarged perspective view of the internal insert shown in FIG. 40.

FIG. 43 is a top view of a portion of an internal insert for a tube according to some embodiments of the present invention.

FIG. 44 is a side view of a an insert according to an embodiment of the present invention, shown within a flat tube in phantom.

FIG. 45 is a side view of another insert according to an embodiment of the present invention, shown within a flat tube in phantom.

FIG. 46 schematically illustrates a set of exemplary manufacturing steps that can be used to form a tube according to some embodiments of the present invention.

FIG. 47 is a partially exploded side view of the tube shown in FIG. 46.

FIG. 48 schematically illustrates a set of exemplary manufacturing steps that can be used to form a tube according to some embodiments of the present invention.

FIG. 49 is a roll press manufacturing line that can be used to manufacture tubes according to some embodiments of the present invention.

FIG. 50 schematically illustrates a set of exemplary manufacturing steps that can be used to form a tube according to some embodiments of the present invention.

FIG. 51 schematically illustrates a set of exemplary manufacturing steps that can be used to form a tube according to other embodiments of the present invention.

FIG. 52 schematically illustrates a set of exemplary manufacturing steps that can be used to form a tube according to still other embodiments of the present invention.

FIG. 53 schematically illustrates a set of exemplary manufacturing steps that can be used to form a tube according to yet other embodiments of the present invention.

FIG. 54 schematically illustrates a set of exemplary manufacturing steps that can be used to form a tube according to other embodiments of the present invention.

FIG. 55 illustrates an exemplary manufacturing line that can be used to manufacture tubes according to some embodiments of the present invention.

FIG. 55A is a sectional view showing a perforation station of the manufacturing line shown in FIG. 55.

FIG. 55B is a side view showing the perforation station shown in FIG. 55A.

FIG. 55C is a sectional view showing a breaking roller and a bar of the manufacturing line shown in FIG. 55.

FIG. 55D is a side view of a breaking roller and a bar of the manufacturing line shown in FIG. 55.

FIG. 56 is a side view of a portion of the perforation station shown in FIG. 55A.

FIG. 57A is a side view showing a sheet of material traveling through a portion of the perforation station shown in FIG. 55A.

FIG. 57B is a top view showing a sheet of material traveling through a portion of the perforation station shown in FIG. 55A.

FIG. 58 is a side view of a breaking roller and a bar of the manufacturing line shown in FIG. 55.

FIG. 59 is a series of schematic end views of the manufacturing line shown in FIG. 55, shown in different stages of forming a flat tube with insert.

FIG. 60 is a schematic top view of a folding roller portion of the manufacturing line shown in FIG. 55.

FIG. 60A is an end view of the folding roller portion shown in FIG. 60.

FIG. 61 is a schematic end view of a finned flat tube manufacturing line according to an embodiment of the present invention.

FIG. 62 is an exploded view of a heat exchanger having finned flat tubes according to all embodiment of the present invention.

FIGS. 63A-C are partial views of fin sets according to different embodiments of the present invention.

FIG. 64 is a schematic view of a finned tube manufacturing process according to an embodiment of the present invention.

FIG. 65 is a perspective side view of a portion of the manufacturing process shown in FIG. 64.

FIG. 66 is a detail view of a heat exchanger having finned flat tubes according to an embodiment of the present invention

FIG. 67 is a detail view of a flat tube that can be used in producing a finned flat tube according to an embodiment of the present invention.

FIG. 68 is a detail side view of a heat exchanger having finned flat tubes according to another embodiment of the present invention

FIG. 69 is a detail perspective view of the part of the heat exchanger shown in FIG. 68.

FIG. 70 is a side view of a collection tank according to an embodiment of the present invention.

FIG. 70A is an end view of the collection tank shown in FIG. 70.

FIG. 71 is a detail view of a heat exchanger having the collection tank illustrated in FIGS. 70 and 70A.

FIG. 72 is a perspective view of a collection tank according to another embodiment of the present invention.

FIG. 73 is a detail perspective view of a heat exchanger having the collection tank illustrated in FIG. 72.

FIG. 74 is another detail perspective view of the heat exchanger shown in FIG. 73.

FIG. 75 is a detail perspective view of the collection tank shown in FIG. 72.

FIG. 76 is another detail view of a heat exchanger having the collection tank illustrated in FIGS. 70-71.

FIG. 77 is an elevational view of the heat exchanger illustrated in FIGS. 71 and 76.

FIG. 78 is a detail side view of a heat exchanger having a collection tank according to another embodiment of the present invention.

FIG. 79 is a detail end view of the heat exchanger illustrated in FIG. 78.

FIG. 80 is a detail side view of the collection tank of the heat exchanger illustrated in FIGS. 78 and 79.

FIG. 80A is an end view of the collection tank illustrated in FIGS. 78-80.

FIG. 81 is a detail side view of a heat exchanger having a collection tank according to another embodiment of the present invention.

FIG. 82 is a detail end view of a heat exchanger having a collection tank according to another embodiment of the present invention.

FIG. 83 is a detail side view of the collection tank of the heal exchanger illustrated in FIG. 81.

FIG. 84 is a flowchart of a heat exchanger manufacturing process according to an embodiment of the present invention.

FIG. 84A is a schematic view of a heat exchanger manufactured according to the flowchart of FIG. 84.

FIG. 85 is an exploded perspective view of a heat exchanger according to another embodiment of the present invention.

FIG. 86 is an exploded perspective view of a heat exchanger according to another embodiment of the present invention.

FIG. 87 is an end view of a flat tube of the heat exchanger illustrated in FIG. 86.

FIG. 88 is an exploded perspective view of a heat exchanger according to another embodiment of the present invention.

FIG. 89 illustrate end views of alternative flat tube embodiments according to the present invention.

FIG. 90 is an exploded perspective view of a heat exchanger according to another embodiment of the present invention.

FIG. 91 are views of a flat tube according to another embodiment of the present invention, shown in different stages of formation.

FIGS. 92-95 illustrate methods of connecting portions of a heat exchanger according to some embodiments of the present invention.

FIG. 96 is a graph showing silicon diffusion depths for heat exchangers connected according to some embodiments of the present invention.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

As described in greater detail below, many embodiments of the present invention relate to or are based upon the use of tubes having a substantially flat cross-sectional shape taken along a plane perpendicular to a longitudinal axis of the tube. In particular, each such tube can have a major dimension and a smaller minor dimension perpendicular to the major dimension. These dimensions are sometimes referred to herein as being “diameters”, although the use of the term “diameter” is not intended to alone indicate or imply that the feature referred to is round, rotund, or otherwise has any particular shape. Rather, the term “diameter” is only used to refer to a largest dimension of the tube in the direction and location indicated. Each such tube can have two opposing walls defining the faces of the tube (referred to herein as the “broad sides” of the tube), and two shorter and more stable walls (referred to herein as the “narrow sides” of the tube) joining the broad sides. Collectively, the broad and narrow sides of the tube define an interior space through which fluid can flow in any state, including without limitation gas, liquid, vapor, and any combination thereof at any pressure or vacuum (including no pressure or vacuum).

Another feature of the flat tubes employed in many embodiments of the present invention (described in greater detail below) is the relatively low thickness of material used to construct at least some of the walls of the flat tubes. In some embodiments, the wall material of the flat tubes has a thickness of no greater than about 0.20 mm (0.007874 in). In still other embodiments, the wall material of the flat tubes has a thickness of no greater than about 0.15 mm (0.0059055 in). The relatively low wall material thickness can result in good thermal properties of the flat tubes. Also, by utilizing one or more of the flat tube features described herein, the inventors have discovered that a number of different flat tubes having various characteristics adapted for a variety of applications can be constructed using significantly reduced material while retaining strength and heat exchange properties of heavier conventional flat tubes. In some embodiments, a wall material thickness of the flat tubes of no less than about 0.050 mm (i.e., no less than about 0.0019685 in) provides good strength and corrosion resistance performance, while in other embodiments, a wall material thickness of the flat tubes of no less than about 0.030 mm (0.00118 in) can be used.

As explained in greater detail below, the heat exchanger tubes and other portions of heat exchangers described herein can be manufactured using a number of manufacturing techniques and processes and can include corrosion protection features, such as, for example, those techniques and processes described below and illustrated in FIGS. 92-95. A number of manufacturing processes and techniques and the corrosion protection features referenced hereinafter are particularly advantageous when applied to heat exchanger tubes and portions of heat exchangers having significantly reduced material thickness. In addition, such techniques, processes, and corrosion protection features provide significant advantages relating to the overall performance of flat tubes and heat exchangers made from such material.

Many embodiments of the present invention utilize flat tubes having major and minor diameters as described above (indicated as D and d, respectively, in the following text) that provide unique advantages in many applications. When used, for example, in conjunction with the material thicknesses just described and in conjunction with other features of the flat tubes described in the various embodiments below, flat tubes adapted for a number of different applications can be produced. Also, the ability to produce flat tubes having some of the major and minor dimensions D, d described herein is facilitated by the use of the relatively thin wall material described above.

For example, in some embodiments of the present invention, the major dimension D (i.e., the width of the flat tube in the illustrated embodiments herein) is no less than about 10 mm (0.39370 in). Also, this major dimension D is no greater than about 300 mm (3.9370 in) in some embodiments. In other embodiments, the major dimension D is no greater than about 200 mm (7.87402 in). As another example, in some embodiments of the present invention, the minor diameter d (i.e., the thickness of the flat tube in the illustrated embodiments herein) is no less than about 0.7 mm (0.02756 in). Also, this minor dimension d is no greater than about 10 mm (0.39370 in) in some embodiments. In other embodiments, the minor dimension d is greater than about 7 mm (0.2756 in). Such major and minor dimensions apply to any of the flat tube embodiments described and/or illustrated herein.

In many embodiments, the major and minor dimensions D, d are dependent at least in part upon the applications of the flat tubes. For example, in condenser applications, the major diameter D of the flat tube is no less than about 10 mm (0.39370 in) in some embodiments. Also, a major diameter D of the flat tube in some condenser applications is no greater than about 20 mm (0.78740 in). The minor diameter d for some condenser applications of the flat tube is no less than about 1.0 mm (0.039370 in). Also, a minor diameter d of the flat tube in some condenser applications is no greater than about 2.0 mm (0.078740 in). As another example, in radiator applications, the major diameter D of the flat tube is no less than about 10 mm (0.39370 in) in some embodiments. Also, a major diameter D of the flat tube in some radiator applications is no greater than about 200 mm (7.8740 in). The minor diameter d for some radiator applications of the flat tube is no less than about 0.7 mm (0.027559 in). Also, a minor diameter d of the flat tube in some radiator applications is no greater than about 2.0 mm (0.078740 in) As another example, in charge air cooler applications, the major diameter D of the flat tube is no less than about 20 mm (0.78740 in) in some embodiments. Also, a major diameter D of the flat tube in some charge air cooler applications is no greater than about 160 mm (6.29921 in). The minor diameter d for some charge air cooler applications of the flat tube is no less than about 4.0 mm (0.15748 in). Also, a minor diameter d of the flat tube in some charge air cooler applications is no greater than about 10.0 mm (0.39370 in).

Still other applications of flat tubes according to any of the embodiments described herein include oil coolers. In oil cooler applications, the major diameter D of the flat tube is no less than about 10 mm (0.49470 in) in some embodiments. Also, a major diameter D of the flat tube in some oil cooler applications is no greater than about 150 mm (5.90551 in). The minor diameter d for some oil cooler applications of the flat tube is no less than about 1.5 mm (0.05906 in). Also, a minor diameter d of the flat tube in some oil cooler applications is no greater than about 4.0 mm (0.15748 in). As yet another example, in evaporator applications, the major diameter D of the flat tube is no less than about 30 mm (1.18110 in) in some embodiments. Also, a major diameter D of the flat tube in some evaporator applications is no greater than about 75 mm (2.95276 in). The minor diameter d for some evaporator applications of the flat tube is no less than about 1.0 mm (0.039370 in). Also, a minor diameter d of the flat tube in some evaporator applications is no greater than about 2.0 mm (0.078740 in). It should be noted that further applications (e.g., gas coolers) of the flat tubes described and/or illustrated herein are possible, and fall within the spirit and scope of the present invention.

Many of the flat tube embodiments described below and illustrated herein are constructed of a metal including aluminum (e.g., aluminum or an aluminum alloy). However, a number of other types of metals can instead be utilized while still providing the strength, heat transfer, and manufacturability characteristics desired for use in heat exchange devices. In some embodiments, the metal material of the flat tubes is provided with a brazing material coating. The brazing material coating can have a number of different possible thicknesses, and in some embodiments is no less than about 10% of the thickness of the flat tube wall material to produce good performance results. Also, in some embodiments, the brazing material coating is no greater than about 30% of the thickness of the flat tube wall material. In other embodiments where the flat tubes are to be soldered rather than brazed, the metal material of the flat tubes can be provided with a soldering material coating. A number of different securing operations (brazing, welding, soldering, and the like) can be used to construct any of the various flat tubes and heat exchanger assemblies described and/or illustrated herein. However, portions of the following text refer only to brazing, although it should be understood that other types of securing operations (including welding and soldering) are equally applicable in such embodiments.

A number of the flat tube features mentioned above relate to the construction of the tube walls using relatively thin sheet material. In some embodiments, significant enhancements to thin-walled flat tube performance is generated by providing either or both of the stable narrow sides with folds that are substantially perpendicular or substantially parallel to the broad sides of the flat tube. Such folds can be formed, for example, by rolling or folding adjacent longitudinal edges of sheet metal upon or into one another. In those embodiments of the present invention in which either or both narrow sides of the flat tube have folds that are substantially parallel to the broad sides of the flat tube, such folds can have the same or different lengths with respect to one another. As will also be described in greater detail below, folds at the narrow sides of a flat tube can be shaped to hook or inter-engage with one another—a feature that can be helpful in the manufacture of the flat tube and/or of a heat exchanger employing the flat tube.

In many of the following embodiments, flat tubes are disclosed having folded narrow sides and also having other folds and/or deformations formed within the flat tubes. In a manufacturing process, the folds that form the narrow sides can be produced subsequent to the manufacture of such other folds and/or deformations, although other manufacturing alternatives are possible. Also, it should be noted that the folds formed within the flat tube can be multiple folds, and in some embodiments are arranged tightly against or abutting one another.

A first embodiment of a flat tube 10 according to the present invention is illustrated in FIGS. 1-5. The flat tube 10 is constructed of two portions of sheet material 12, 14 shaped to define internal flow channels 16. Each of the two portions 12, 14 can be formed from one endless strip of material or coil passed through a manufacturing line having a material cutting device (e.g., laser, saw, water jet, blade, and the like) for producing two strips that are then joined together as will be described below. Alternatively, the two portions 12, 14 can be formed from two endless strips of material or coils passed through a manufacturing line. In either case, the manufacturing line can be equipped with roll sets (as illustrated by way of example below) or other sheet forming elements to shape the strips as will be described in greater detail below. As used herein and in the appended claims, the term “endless” does not literally mean that the element or product referred to has a limitless supply. Rather, the term “endless” means only that the element or product is received from a much greater supply of continuous material in some upstream bulk form, such as in supply coils of material.

Although the portions 12, 14 can have thicknesses falling within any of the ranges described above, the portions 12, 14 in the illustrated embodiment of FIGS. 1-5 have a wall thickness of about 0.10 mm (0.0039369 in) by way of example. In some embodiments, the portions 12, 14 include material formed of aluminum or an aluminum alloy. However, other portion materials (described above) can instead be utilized in other embodiments. Either or both sides of the portions 12, 14 can be coated with a brazing material coating, such as a layer of brazing coating that is about 10-30% of the portion thickness.

As shown in FIG. 2, the flat tube 10 of the illustrated embodiment defines a small diameter d. Using the wall thicknesses described earlier, the inventors have discovered that a small diameter d of at least about 0.8 mm (0.031496 in) provides good performance results in many applications. Also using the wall thicknesses described earlier, the inventors have discovered that a small diameter d of no greater than about 2.0 mm (0.07874 in) provides good performance results in many applications. However, in some embodiments, a maximum small tube diameter d of no greater than about 1.5 mm (0.059055 in) is used. As shown in FIG. 1, the flat tube 10 of the illustrated embodiment also defines a large diameter D. Using the wall thicknesses described earlier, the inventors have discovered that a large diameter D of at least about 40 mm (1.5748 in) provides good performance results in many applications. Also using the wall thicknesses described earlier, the inventors have discovered that a large diameter D of no greater than about 45 mm (1.7717 in) provides good performance results in many applications. However, it is possible for the flat tube 10 to define a large diameter D and a small diameter d with other dimensions, including those described above with reference to all of the flat tubes disclosed herein, based at least in part upon the manufacturing processes used, the intended application of the tubes, and/or the use of thicker or thinner wall materials. For this purpose, the portions 12, 14 of particular widths can be made available, and the installations of the manufacturing line can be adjusted according to the desired diameters D and d.

The flat tube 10 in the illustrated embodiment of FIGS. 1-5 includes a first narrow side 18, a second narrow side 20, a first broad side 22, and a second broad side 24. The first broad side 22 and the second broad side 24 correspond to the portions 12 and 14, respectively. With particular reference to FIG. 1, the first broad side 22 and the second broad side 24 define a number of folds 28. The folds 28 extend from the first broad side 22 and the second broad side 24 to define four flow channels 16. In other embodiments, the flat tube 10 can include more or fewer flow channels 16 defined between the folds 28. Although the folds 28 can run in an uninterrupted and continuous manner along the entire length of the flat tube 10 to isolate adjacent flow channels 16 from one another. However, in other embodiments, the folds 28 can be interrupted or breached in one or more locations along their length in order to permit flow between flow channels 16. Regardless of whether the folds 28 are uninterrupted or interrupted, the folds 28 can strengthen the flat tube 10 against compression, and can strengthen the flat tube 10 against expansion in those embodiments in which the distal ends of the folds 28 are attached to a broad side 24 of the flat tube 10 (e.g., by brazing or in any other suitable manner). The folds 28 can also serve a rigidifying function in order to resist bending of the flat tube 10.

With reference now to FIGS. 1 and 2, the first broad side 22 and the second broad side 24 also define a number of protrusions 26. In other embodiments, neither side 22, 24 has such protrusions 26. The illustrated protrusions are generally convex bumps extending into the flow channels 16 of the flat tube 10, and can have any footprint desired, such as a round footprint, square, triangular or other polygonal footprint, any elongated footprint (e.g., elongated ribs running along any desired length of the flow channels, running transverse to the flow channels, and the like), irregular footprints, or footprints of any other shape (e.g., serpentine, zig-zag, chevron, and the like). Where used, the protrusions 26 can function to induce or sustain turbulence in the flat tube 10, thereby increasing heat transfer in such locations. Also, like the folds 28 described above, the protrusions 26 can serve a rigidifying function to help stiffen the broad sides 22, 24 of the flat tube 10. The protrusions 26 can be located in any pattern or patternless manner in the flat tube 10, and in some embodiments are located only in particular areas of the flow channels 16 to produce desired flow and heat transfer effects.

FIG. 3 schematically illustrates a set of exemplary manufacturing steps that can be used to form a flat tube 10 such as that illustrated in FIGS. 1, 2, 4, and 5. Starting with a first portion of material 12 defining a width W and a second portion of material 14 defining a smaller width w, a desired number of folds 28 are formed, and will help to define the flow channels 16. The folds 28 in the illustrated embodiment are formed on both portions 12, 14. In other embodiments, folds 28 are formed in only one of the portions 12, 14. Similarly, the protrusions 26 in the illustrated embodiment are formed on both portions 12, 14, although in other embodiments the protrusions 26 are formed in only one of the portions 12, 14. The folds 28 and protrusions 26 are located between the longitudinal edges of the material defining the portions 12, 14 (e.g., the longitudinal edges of the sheet metal defining the portions 12, 14).

The width W of the first portion 12 and the width w of the second portion 14 in the illustrated embodiment of FIGS. 1-5 are reduced during the course of forming the folds 28 and protrusions 26. It is to be understood that other deformations can be included in the exemplary manufacturing steps of FIG. 3 to generate other features of the flat tube 10, as desired. With continued reference to the manufacturing example of FIG. 3, an additional set of folds 30 is formed at each of the longitudinal edges of the portions 12, 14 subsequent to forming the necessary folds 28 and protrusions 26, thereby defining the narrow sides 18 and 20 of the flat tube 10. In other embodiments, either or both of the additional sets of folds 30 can be produced prior to or at the same time as the folds 28 and protrusions 26, although the process illustrated in FIG. 3 can provide significant manufacturing advantages based upon manufacturing line setup and operation. As best illustrated in FIGS. 4 and 5, the additional folds 30 of each of the portions 12, 14 engage one another to define the first narrow side 18 and the second narrow side 20 of the tube, respectively. By virtue of this engagement between the longitudinal edges of the portions 12, 14 of the two-piece flat tube 10, the portions 12, 14 can be held together even before the brazing or other securing operations on the portions 12, 14. More specifically, FIGS. 4 and 5 illustrate the folds 30 of one portion 14 defining a larger length than the folds 30 of the other portion 12. Thus, the folds 30 of one portion 12 can fold around the folds 14 of the other portion, as is also shown in FIG. 2.

As the illustrated embodiment of FIGS. 1-5 shows, in some embodiments, one of the portions 12 is sufficiently long to wrap around and thereby receive the longitudinal edge of the other portion 14 (e.g., whereby the longitudinal edge of one portion 14 is nested in the folded longitudinal edge of the other portion 12. In other embodiments, one of the portions 12 is instead only sufficiently long to overlap the longitudinal edges of the other portion 14. However, the embodiments described above in connection with FIGS. 1-5 can provide significant advantages relating to the assembly and manufacture of the flat tube 10, including the retention of the portions 12, 14 as described above, and a greater degree of narrow side reinforcement and strength based upon the greater thickness of material at the narrow sides 18, 20. In the illustrated embodiment of FIGS. 1-5, both narrow sides 18, 20 are provided with the same folded structure best show in FIGS. 2-5. However, in other embodiments, only one of the two narrow sides 18, 20 of the flat tube 10 has any of the folded structures described above. In such embodiments, the connection between the two portions 12, 14 at the other narrow side 20, 18 can be made in any other manner desired.

FIGS. 6-11 illustrate alternative constructions of flat tubes according to additional embodiments of the present invention. These embodiments employ much of the same structure and have many of the same properties as the embodiments of the flat tube described above in connection with FIGS. 1-5. Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiments described above in connection with FIGS. 1-5. Reference should be made to the description above in connection with FIGS. 1-5 for additional information regarding the structure and features, and possible alternatives to the structure and features of the flat tubes illustrated in FIGS. 6-11 and described below. Structure and features of the embodiments shown in FIGS. 6-11 that correspond to structure and features of the embodiments of FIGS. 1-5 are designated hereinafter in respective hundreds series of reference numbers (e.g., 112, 212, 312, and the like).

FIGS. 6-11 illustrate other constructions of a narrow side 118, 218, 318, 418, 518, 618 and/or 120, 220, 320, 420, 520, 620. For ease of description, reference herein is made only to one of the narrow sides 118, 218, 318, 418, 518, 618 of each tube 110, 210, 310, 410, 510, 610, it being understood that the other narrow side 120, 220, 320, 420, 520, 620 can have the same or different structure, as desired. The narrow sides 118, 218, 318, 418, 518, 618 shown in FIGS. 6-11 can be manufactured in steps similar to those described above with reference to FIG. 3. Furthermore, each of the narrow sides 118, 218, 318, 418, 518, 618 shown in FIGS. 6-11 provide strength and/or stability to the tube 110, 210, 310, 410, 510, 610 compared with conventional flat tube designs, taking into consideration the relatively small thickness of the material used to construct the tube walls in some embodiments: about 0.050-0.15 mm (0.0019685-0.0059055 in) in some embodiments as described above, and about 0.030-0.15 mm (0.00118-0.0059055 in) in other embodiments, and other material thickness ranges described herein.

The narrow sides 118, 218, 418 of the flat tubes 110, 210, 310 shown in FIGS. 6, 7, and 9 can be formed by folding or rolling together adjacent longitudinal edges of the two tube portions 112, 212, 412 and 114, 214, 414, thereby defining a number of folds 130, 230, 330, 430, 530, 630. It should be noted that forms are referred to herein and in the appended claims as “folds” regardless of whether they were made by rolling or folding operations, and regardless of whether the resulting shapes are rotund (e.g., FIG. 6), stacked (e.g., FIGS. 7-9) or angular (e.g., FIGS. 10 and 11). With continued reference to FIGS. 6, 7, and 9, each narrow side 118, 218, 418 provides unique heat transfer, strength, and stability characteristics, and can be formed using different techniques. At least a portion of the folded or rolled longitudinal edges (and in the case of the narrow sides 218, 418 illustrated in FIGS. 7 and 9, the majority of the folded or rolled longitudinal edges) are formed to be approximately perpendicular to the broad sides 122, 222, 422 and 124, 224, 424 of the flat tube 110, 210, 410.

With reference to the narrow sides 518, 618 of the flat tubes 510, 610 shown in FIGS. 10 and 11, the longitudinal edges of portions 512, 612 and 514, 614 can also be formed by folding or rolling together the adjacent longitudinal edges of the two tube portions 512, 612 and 514, 614. Once again, each of the narrow sides 518, 618 of the flat tubes 510, 610 provides unique heat transfer, strength, and stability characteristics, and can be formed using different techniques. In both cases, the longitudinal edges of the portions 512, 612 and 514, 614 can be folded upon itself to define a serpentine edge of the flat tube 510, 610. Although the folds 530, 630 of this serpentine edge can abut one another with little or no space between adjacent folds 530, 630, in some embodiments (see FIGS. 10 and 11), a space exists between adjacent portions of each fold. The heat transfer, firmness, strength, and/or size of the flat tubes 510, 610 can be selected as desired, based upon the orientation of the folds 530, 630 in such embodiments (e.g., substantially perpendicular to the broad sides 522, 622 and 524, 624, or at a significant angle less than 90 degrees with respect to the broad sides 522, 622 and 524, 624) and the space between adjacent portions of each fold 530, 630.

The illustrated embodiment of FIG. 8 provides an example of how at least a portion of the folds 330 (and in some cases, the majority of the folds 330) of the narrow side 318 can be parallel or substantially parallel to the broad sides 322, 324 of the flat tube 310. Some or all of these folds 330 can lie against one another for improved heat transfer therebetween. In some embodiments, the folds 330 of the narrow side 318 can be substantially the same length L, such as in cases where a particular flow channel shape is desired adjacent the narrow side 318 of the flat tube 310. However, in other embodiments (such as that shown in FIG. 8), at least some of the narrow side folds 330 parallel to the broad sides 322, 324 have a different length than others. For example, the differently-sized folds can define a generally concave (FIG. 8) or convex side of an adjacent flow channel 316, such as for defining a desired flow channel shape adjacent the narrow side 318. With reference to the illustrated embodiment of FIG. 8, the length L of each fold 330 decreases from the outside of the flat tube 310 towards the inside of the flat tube 310 (i.e., the first fold 330 that lies against the broad side 322 has a greater length L than the subsequent fold 330, and the last fold 330 that lies against the other broad side 324 has a greater length L than the previous fold 330). In these embodiments, such shapes of the narrow side 318 can help avoid sudden temperature transitions across the flat tube 310, an issue that can otherwise contribute to tube failure in many applications. As another example, differently-sized folds can define a wedge-shaped narrow side 318, which can provide a non-symmetrical heat transfer bridge across the distance between the broad sides 322, 324. Still other shapes of the narrow side 318 defined by differently-sized folds 330 parallel to the broad sides 322, 324 are possible, and fall within the spirit and scope of the present invention.

In those embodiments in which folds 330 of the narrow side 318 are parallel or substantially parallel to the broad sides 322, 324 of the two-piece flat tube 310, the folds 330 formed of the first portion 312 can be hooked together or inter-engaged with the folds 330 formed of the second portion 314 (see FIG. 8, for example). As a result, the formed flat tube 310 can be held together before brazing or other securing operations on the portions 312, 314, which can facilitate assembly of the flat tubes 310 into banks and/or of heat exchangers having such flat tubes 310, as it is further explained below. It will be appreciated that similar advantages exist in the other narrow side embodiments described above with reference to FIGS. 6, 7, and 9-11.

In those embodiments of the present invention in which either or both narrow sides 18, 118, 218, 318, 418, 518, 618, 20, 120, 220, 320, 420, 520, 620 have folds 30, 130, 230, 330, 430, 530, 630 as described above, such folds 30, 130, 230, 330, 430, 530, 630 can generally provide increased stability to the narrow sides 18, 118, 218, 318, 418, 518, 618, 20, 120, 220, 320, 420, 520, 620 despite the relatively small wall thickness of the flat tube 10, 110, 210, 310, 410, 510, 610 mentioned earlier. A greater number of folds 30, 130, 230, 330, 430, 530, 630 at the narrow sides 18, 118, 218, 318, 418, 518, 618, 20, 120, 220, 320, 420, 520, 620 can also provide better protection for the flat tube 10, 110, 210, 310, 410, 510, 610 against damage due to high internal pressures, impact from objects, and corrosion, for example. This can be of great importance when using such flat tubes 10, 110, 210, 310, 410, 510, 610 in heat exchangers for motor vehicles.

Although not required in the flat tube embodiments described above, the first and/or second portions 12, 112, 212, 312, 412, 512, 612 and 14, 114, 214, 314, 414, 514, 614 can have one or more folds 28 located between the narrow sides 18, 118, 218, 318, 418, 518, 618 and 20, 120, 220, 320, 420, 520, 620 of the flat tube 10, 110, 210, 310, 410, 510, 610. In this regard, the description of such folds 28 in the illustrated embodiment of FIGS. 1-5 is applicable equally to the other embodiments described above. For ease of description, further information regarding these folds 28 will now be made with reference to the illustrated embodiments of FIGS. 12 and 13 using the reference numbers of the embodiment of FIGS. 1-5.

In some embodiments, the inventors have discovered that locations of the internal folds 28 can be selected to define flow channels 16 of varying size to enable different fluid and/or flow characteristics (e.g., flow rates and/or directions, pressures, multiple fluid types, and the like) in different locations of the same flat tube 10, and to enable different manners of heat transfer in the different locations. With reference to the illustrated embodiment of FIG. 12, the width or distance “a” between interior folds 28 is defined substantially parallel to the first and second broad sides 22, 24 of the flat tube 10, and varies based upon the desired degree of resistance to temperature change along the width of the flat tube 10.

In some embodiments, such as that shown in FIG. 12, the distance “a” between interior folds 28 can become larger starting from either or both narrow sides 18 and 20 of the flat tube 10 toward the center of the flat tube 10. Accordingly, in some embodiments, the distance “a” increases from interior fold 28 to interior fold 28, starting from one narrow side 18, 20 in the direction of the middle of the flat tube 10, and subsequently decreases again in the direction of the other narrow side 20, 18. In such embodiments, the cross-sectional area of the individual flow channels 16 formed by the interior folds 28 increases and decreases, respectively. In some embodiments, the distance “a” begins at either or both narrow sides 18, at a magnitude of about 0.5 mm (0.019685 in) and increments to a few millimeters.

For example, in such cases, a flat tube 10 with a width of approximately 42 mm (approx. 1.6634 in) can include a large number of interior folds 28 and flow channels 16. It is conceivable that a flat tube 10 can include relatively wider flow channels 16 substantially adjacent either or both narrow sides 18, 20, with narrower flow channels 16 near the center of the flat tube 10. Also, although the flow channels 16 in many embodiments have widths “a” of the sizes described above, such widths can be significantly larger in other embodiments, including ranges of at least 1 cm (0.3937 in).

In some embodiments, the flat tube 10 can include interior folds 28 immediately adjacent one another, wherein such interior folds are abutting or in intimate contact with one another immediately following formation of the interior folds 28 or after brazing or other securing operations on the portions 12, 14. For example, multiple interior folds 28 can be arranged tightly against one another. In any of these cases, two or more interior folds 28 can define a set 32 of interior folds 28. The flat tube 10 can have any number of such sets 32 of interior folds 28, such as those shown in FIG. 13, either alone or in conjunction with any number of single folds 28. Each set 32 of interior folds 28 shown in FIG. 13 includes three individual interior folds 28. However, in other embodiments, two interior folds 28 can be sufficient to form a set 32, and/or four or more interior folds 28 can form a set 32. Accordingly, the number of interior folds 28 that form the set 32 is freely selectable based upon the intended application of the flat tube 10 and other factors. In this regard, either or both portions 12, 14 of the flat tube 10 can have fold sets 32 having any number of interior folds 28 and any combination of sets 32 with different numbers of interior folds 28.

The single interior folds 28 and/or sets 32 of interior folds 38 can all be located on the same portion 12 or 14, or on both portions 12, 14 of the flat tube 10 in any arrangement desired. For example, multiple sets 32 of interior folds 28 can be symmetrically arranged about a central location of the flat tube 10 (such as the arrangement of interior fold sets 32 shown in FIG. 13), wherein corresponding sets 32 on opposite sides of the central location extend from the same portion 12, 14 or from a different portion 12, 14 (e.g., FIG. 13). Also, in some embodiments, one or more single interior folds 28 and/or one or more sets 32 of interior folds 28 on one portion 12, 14 of the flat tube 10 can be nested within the interior folds 28 of a set 32 on the opposite portion 14, 12 of the flat tube 10.

Sets 32 of interior folds 28 as described above can be utilized to provide flat tubes 10 with higher resistance to pressure and greater load-bearing capacity, and can also be used to vary the cross-sectional shape of flow channels 16. It should be noted that the features described above regarding varying flat tubes 10 with varying flow channel widths apply equally to embodiments in which sets 32 of interior folds 28 are utilized. Also, in those embodiments in which the flat tube 10 is formed with a brazing process, the interior folds 28 on one broad side 22, 24 (whether in single form or in sets 32) can form brazed joints with the other broad side 24, 22, thus improving bonding within the flat tube 10.

FIGS. 14 and 15 illustrate two additional constructions of flat tubes according to additional embodiments of the present invention. These embodiments employ much of the same structure and have many of the same properties as the embodiments of the flat tube described above in connection with FIGS. 1-13. Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiments described above in connection with FIGS. 1-13. Reference should be made to the description above in connection with FIGS. 1-13 for additional information regarding the structure and features, and possible alternatives to the structure and features of the flat tubes illustrated in FIGS. 14 and 15 and described below. Structure and features of the embodiments shown in FIGS. 14 and 15 that correspond to structure and features of the embodiments of FIGS. 1-13 are designated hereinafter in the 700 and 800 series of reference numbers, respectively.

The flat tubes 10, 110, 210, 310, 410, 510, 610 illustrated in FIGS. 1-13 above each have internal walls defined by interior folds 28 of the first and/or second portions 12, 112, 212, 312, 412, 512, 612, 14, 114, 214, 314, 414, 514, 614. In any of these embodiments, however, these walls at least partially defining the flow channels 16, 116, 216, 316, 416, 516, 616 can be defined by a separate portion of material that is connected to either or both of the first and second portions 12, 112, 212, 312, 412, 512, 612, 14, 114, 214, 314, 414, 514, 614 in the manufacture of the flat tubes 10, 110, 210, 310, 410, 510, 610. Although different from the flat tubes 10, 110, 210, 310, 410, 510, 610 described above in this manner, such alternative flat tubes can have any of the construction features described above in connection with FIGS. 1-13 (e.g., exterior wall thicknesses and materials, tube diameters, interior wall shapes, locations, spacings, and sets, and narrow side constructions).

For example, the flat tubes 710, 810 shown in FIGS. 14 and 15 are each constructed using two portions 712, 714 and 812, 814, respectively between and which is located an insert 734, 834 defined by another portion of material. In both cases, the insert 734, 834 has a corrugated shape, whereby corrugations of the insert 734, 834 can form flow channels 716, 816 in the flat tube 710, 810. Either or both narrow sides 718, 720 and 818, 820 of the flat tube 710, 810 (only one of which is shown in each of FIGS. 14 and 15) can incorporate a portion of the insert 734, 834 by commonly folding the edges of the first and second portions 712, 714 and 812, 814 with the edges of the insert 734, 834. For example, in some embodiments, the flat tube 710 has serpentine narrow sides 718, 720 as shown in FIG. 14, wherein the edges of the insert 734 are folded with and into the longitudinal sides of the first and second portions 712, 714. In other embodiments, the narrow sides 818, 820 of the flat tube 810 are folded tightly against one another as shown in FIG. 15, wherein the edges of the insert 834 are again folded with and into the longitudinal sides of the first and second portions 812, 814. In yet other embodiments, the longitudinal edges of an insert can be rolled into those of the first and second portions in any of the narrow side structures shown in FIGS. 6-10.

The embodiments of the present invention described above each utilize two separate pieces of material to define the first and second portions 12, 112, 212, 312, 412, 512, 612, 712, 812, and 14, 114, 214, 314, 414, 514, 614, 714, 814 of the flat tubes 10, 110, 210, 310, 410, 510, 610, 710, 810. Although such tube constructions have unique advantages, including some portion-to-portion inter-engagement features and manufacturing advantages, flat tubes according to the present invention can also be formed of one part, such as by a single or undivided endless sheet metal strip. By deforming the single part, free longitudinal edges of the single part can be brought together and joined by brazing, welding, or other securing operations. In other words, some embodiments of the flat tubes according to the present invention can be formed from one part (e.g., sheet metal strip) while still defining two stable narrow sides. Various embodiments of such one-part flat tubes are described in detail below. With the exception of those features of the one-part flat tubes described below that are inconsistent or incompatible with the tube features described above with reference to the two-piece embodiments of FIGS. 1-15, the one-part flat tubes described below can have any of the construction features described above in connection with FIGS. 1-15 (e.g., exterior wall thicknesses and materials, tube diameters, interior wall shapes, locations, spacings, and sets, and narrow side constructions).

The one-piece tubes described below can have improved thermal properties over conventional flat tubes based at least in part upon the use of the relatively thin tube wall material (described above) that can be employed. Additionally, assembly of the flat tubes within a heat exchanger can also be simplified.

Like the two-piece flat tubes described above, folds formed at the narrow sides of the one-piece flat tubes described below can be substantially perpendicular or substantially parallel to the broad sides. For example, a first narrow side of the flat tube can be formed of a continuous portion of a single sheet of metal and can include a set of multiple folds. In some embodiments, these folds can define multiple lengths (e.g., similar to those described above in connection with FIG. 8), which can help avoid the formation of cracks due to thermal fatigue. A second narrow side of the flat tube can be formed by the free longitudinal edges of the single sheet of metal, and can also have multiple folds. In spite of the sheet metal thickness of 0.05-0.15 mm (0.0019685-0.00591 in) in some embodiments, and 0.03-0.15 mm (0.00118-0.00591 in) in other embodiments, the longitudinal edges of the single piece of material forming the second narrow side can be coupled by brazing, welding, or other securing operations. Also like the two-piece flat tubes described above, either or both broad sides of the one-piece flat tubes can include interior folds and other deformations (e.g., inwardly-directed beads, ribs, or other protrusions that need not reach across the interior of the flat tubes). The interior folds can form flow channels within the flat tube, and can be arranged in any of the manners described above with reference to the two-piece flat tubes. By way of example only, the interior folds can be in sets, can be at particular spacings that may or may not vary across the width of the flat tube, and can increase in the direction from either or both narrow sides toward the middle of the flat tube. As a result of such interior folds and interior fold arrangements, the capability of the one-piece flat tube to resist high temperature change loads can be significantly improved.

Examples of one-piece flat tubes having some of these features are illustrated in FIGS. 16-24, each of which have first and second portions 912, 914, 1012, 1014, 1112, 1114, 1212, 1214, 1312, 1314, 1412, 1414, 1512, 1514, 1612, 1614, 1712, 1714 formed of a common piece of material folded to the shapes illustrated. Although other materials and material thicknesses can be employed as described in greater detail above in connection with the two-piece flat tubes, the illustrated first and second portions 912, 914, 1012, 1014, 1112, 1114, 1212, 1214, 1312, 1314, 1412, 1414, 1512, 1514, 1612, 1614, 1712, 1714 are formed of aluminum or aluminum alloy sheet metal strip having a material thickness of about 0.10 mm (0.003937 in). Any of the flat tubes 910, 1010, 1110, 1210, 1310, 1410, 1510, 1610, 1710 can have a brazing material coating on either or both sides, wherein each layer of the brazing material coating can have a thickness of about 10-20% of the thickness of the sheet metal strip.

Using the wall thicknesses described earlier, the inventors have discovered that a small diameter d of at least 0.8 mm (0.031496 in) for the illustrated flat tubes 910, 1010, 1110, 1210, 1310, 1410, 1510, 1610, 1710 provides good performance results in many applications. Also using the wall thicknesses described earlier, the inventors have discovered that a small diameter d of no greater than about 2.0 mm (0.07874 in) for the illustrated flat tubes 910, 1010, 1110, 1210, 1310, 1410, 1510, 1610, 1710 provides good performance results in many applications. However, in some embodiments, a maximum small diameter d of no greater than about 1.5 mm (0.059055 in) for the illustrated flat tubes 910, 1010, 1110, 1210, 1310, 1410, 1510, 1610, 1710 is used. Moreover, a large diameter D for any of the illustrated flat tubes 910, 1010, 1110, 1210, 1310, 1410, 1510, 1610, 1710 is usually freely selectable within certain manufacturing limits. In some embodiments, one example, the large diameter D is approximately 50 mm (1.969 in). However, one-piece flat tubes 910, 1010, 1110, 1210, 1310, 1410, 1510, 1610, 1710 having larger or smaller diameters D, d (including those described above with regard to all flat tube embodiments disclosed herein) and the wall thicknesses described earlier can also be manufactured, in which cases the original width W of the material (see FIG. 16, for example) used to form the flat tubes 910, 1010, 1110, 1210, 1310, 1410, 1510, 1610, 1710 is made available at the manufacturing line.

As mentioned above, the various types of narrow side folds and interior folds described in connection with the embodiments of FIGS. 1-15 can be employed in the one-piece tubes described herein. In some one-piece tube embodiments, such as those shown in FIGS. 19-24, either or both narrow sides 1218, 1220, 1318, 1320, 1418, 1420, 1518, 1520, 1618, 1620, 1718, 1720 of the flat tube 910, 1010, 1110, 1210, 1310, 1410, 1510, 1610, 1710 can include multiple folds 1230, 1330, 1430, 1530, 1630, 1730, which can provide relatively more stable and strong narrow tube sides 1218, 1220, 1318, 1320, 1418, 1420, 1518, 1520, 1618, 1620, 1718, 1720. As a result, the relatively more stable narrow sides 1218, 1220, 1318, 1320, 1418, 1420, 1518, 1520, 1618, 1620, 1718, 1720 can provide sufficient protection of the flat tubes 910, 1010, 1110, 1210, 1310, 1410, 1510, 1610, 1710 against damage due to temperature and/or pressure fatigue, impact from objects, and corrosion, thereby providing better performance when used in a heat exchanger for motor vehicles (for example).

With reference now to FIG. 16, an example of the manner in which a one-piece tube 910 can be manufactured is shown. In particular, FIG. 16 illustrates at least part of a manufacturing process to form a one-piece flat tube 910. Single and/or multiple folds are made in a sheet of starting material, and will at least partially define interior folds 928 of the flat tube 910, and flow channels 916 within the flat tube 910. In some embodiments, the sheet of starting material is an endless sheet, such as that fed from a coil of material upstream of the manufacturing elements used to produce the folds. At the same or different time, additional folds are created that will at least partially define folds at a narrow side 920 of the flat tube 910. For example, a set 932 of multiple folds 930 is produced at or near the center of the one-piece metal strip illustrated in FIG. 16 to define a narrow side 920 by folding the strip in the direction shown by arrow substantially adjacent the set 932 of multiple folds 930. As a result of this fold indicated by arrow, first and second broad sides 912, 914 of the flat tube 910 are defined. The other narrow side 918 and the folds 930 of the other narrow side 918 can take any of the forms shown in FIGS. 19-23 or those described and/or illustrated above in connection with the narrow sides of the two-piece flat tubes 10, 110, 210, 310, 410, 510, 610, 710, 810. FIGS. 17 and 18 illustrate features of alternate one-piece flat tube constructions (narrow sides not shown) that can be employed. More specifically, FIG. 17 provides an example of how single interior folds 1028 and sets 1032 of multiple interior folds 1028 on either or both broad sides 1022, 1024 can be utilized in the same one-piece flat tube 1010 to define flow channels 1016 of the same or different size. FIG. 18 provides an example of how a number of single interior folds 1128 can be made at particular locations on either or both broad sides 1122, 1124 to define flow channels 1116 of varying cross-sectional size, such as gradually increasing cross-sectional sizes in a direction along the width of the one-piece flat tube 1110.

FIGS. 19-24 show still further examples of one-piece flat tubes 1210, 1310, 1410, 1510, 1610 according to other embodiments of the preset invention. Like the one-piece tube embodiments illustrated in FIGS. 16-18, each of the one-piece flat tubes 1210, 1310, 1410, 1510, 1610 illustrated in FIGS. 19-24 have interior folds 1228, 1328, 1428, 1528, 1628, 1728 arranged individually and/or in sets to define flow channels 1216, 1316, 1416, 1516, 1616, 1716. In some cases, the arrangement of individual interior folds 1228, 1328, 1428, 1528, 1628, 1728 and/or sets 1232, 1332, 1532 of such folds 1228, 1328, 1528 is determined based upon one or more factors (e.g., single or multiple fluids through the tubes 1210, 1310, 1410, 1510, 1610, 1710 anticipated temperatures, thermal stresses, and thermal cycling to which the different portions of the tube width and/or length will be exposed, internal fluid pressures, and the like.

With particular reference first to FIG. 19, multiple interior folds 1228 near the center of the flat tube 1210 define a material thickness of four times that of the unfolded tube material (i.e., two single folds 1228 arranged tightly or immediately adjacent one another, such as in an abutting fashion). The one-piece flat tube 1210 illustrated in FIG. 19 has two such sets 1232 of interior folds 1228, each of which is formed in a different broad side 1222, 1224 of the flat tube 1210. In the embodiment of FIG. 20, four sets 1332 of multiple interior folds 1328 each define a material thickness of six times that of the unfolded tube material (i.e., three single folds 1328 arranged tightly or immediately adjacent one another, such as in an abutting fashion). The interior folds 1328 in the embodiment of FIG. 20 are positioned to define flow channels 1316 of varying size, unlike those of FIG. 19, which have substantially the same size. It will be appreciated that any other number of interior fold sets 1232, 1332 can be provided on either or both broad sides 1222, 1224, 1322, 1324 of the one-piece flat tubes 1210, 1310 illustrated in FIGS. 19 and 20, with or without additional individual interior folds 1228, 1328 (i.e., interior folds 1228, 1328 not in sets 1232, 1332 as also shown in FIGS. 19 and 20).

The embodiments of FIGS. 21, 22, and 23 provide examples of one-piece flat tubes 1410, 1510, 1610 in which only single folds 1428, 1528, 1628 are used to form the flow channels 1416, 1516, 1616. By way of example, the interior folds 1428, 1528 of the one-piece flat tubes 1410, 1510 illustrated in FIGS. 21 and 22 are positioned to define flow channels 1416, 1516 of varying size (increasing toward the center of each flat tube 1410, 1510, 1610), unlike those of FIG. 23, which have substantially the same size, with the exception of a slightly larger flow channel 1616 immediately adjacent either or both narrow sides 1618, 1620. It should be noted that the interior folds 1228, 1328, 1428, 1528, 1628, 1728 of any of the one-piece flat tubes 1210, 1310, 1410, 1510, 1610, 1710 illustrated in FIGS. 19-24 can be positioned to define flow channels 1216, 1316, 1416, 1516, 1616, 1716 of the same or different size, and that the widths of the flow channels 1216, 1316, 1416, 1516, 1616, 1716 can increase or decrease toward the center of the flat tubes 1210, 1310, 1410, 1510, 1610, 1710 gradually in the same direction across the majority or all of the tube width, or in any other manner desired. Also, other constructions of the flat tubes 1210, 1310, 1410, 1510, 1610, 1710 can include different numbers of single folds 1228, 1328, 1428, 1528, 1628, 1728 and sets of multiple interior folds 1228, 1328, 1428, 1528, 1628, 1728 as desired.

With continued reference to the one-piece flat tube embodiments illustrated in FIGS. 19-24, each flat tube 1210, 1310, 1410, 1510, 1610, 1710 has one narrow side 1220, 1320, 1420, 1520, 1620, 1720 defined by a continuous folded portion of the sheet of material used to construct the flat tube 1210, 1310, 1410, 1510, 1610, 1710, and an opposite narrow side 1218, 1318, 1418, 1518, 1618, 1718 where two free longitudinal edges of the sheet of material are brought together and folded to close the flat tube 1210, 1310, 1410, 1510, 1610, 1710. This opposite narrow side 1218, 1318, 1418, 1518, 1618, 1718 and the folds 1230, 1330, 1430, 1530, 1630, 1730 of the opposite narrow side 1218, 1318, 1418, 1518, 1618, 1718 can take any of the forms shown in FIGS. 19-24 or those described and/or illustrated above in connection with the narrow sides of the two-piece flat tubes 10, 110, 210, 310, 410, 510, 610, 710, 810.

With regard to the narrow side 1220, 1320, 1420, 1520, 1620, 1720 formed by the continuous folded portion as described above, this narrow side can take any of the forms shown in FIGS. 19-24. However, this same narrow side 1220, 1320, 1420, 1520, 1620, 1720 can also take any of the shapes described and/or illustrated above in connection with the narrow sides of the two-piece flat tubes 10, 110, 210, 310, 410, 510, 610, 710, 810, in which cases the terminal ends of the first and second portions 12, 14, 112, 114, 212, 214, 312, 314, 412, 414, 512, 514, 612, 614, 712, 714, 812, 814 at the narrow sides 18, 118, 218, 318, 418, 518, 618, 718 of the flat tubes 10, 110, 210, 310, 410, 510, 610, 710, 810 would be joined as part of the same continuous piece of sheet material. Accordingly, the unique benefits of each narrow side form described above in connection with FIGS. 1-11, 14, and 15 can exist for either or both narrow sides 1218, 1220, 1318, 1320, 1418, 1420, 1518, 1520, 1618, 1620, 1720 of the embodiments illustrated in FIGS. 19-24.

With particular reference to the illustrated embodiment of FIG. 19, the one-piece flat tube 1210 illustrated therein has narrow sides 1218, 1220 formed with folds 1230 that are arranged substantially perpendicularly to the broad sides 1222, 1224 of the flat tube 1210. The multiple folds 1230 forming the narrow sides 1218, 1220 are differentiated from each other in that the folds 1230 forming the second narrow side 1220 are formed from a continuous portion of the one-piece strip of material used to create the flat tube 1210, while the folds 1230 forming the first narrow side 1218 are formed from the two longitudinal edges of the one-piece strip of material. In other embodiments, however, the flat tube 1210 can instead have first and second narrow sides 1218, 1220 with folds 1230 that are substantially parallel to the broad sides 1222, 1224 of the flat tube 1210.

The one-piece flat tube 1310 illustrated in FIG. 20 also has a second narrow side 1320 with multiple folds 1330 substantially perpendicular to the broad sides 1322, 1324 of the flat tube 1310, whereas the first narrow side 1318 has multiple folds 1330 arranged substantially parallel to the broad sides 1322, 1324 of the flat tube 1310. In other embodiments, however, the flat tube 1310 can instead have a first narrow side 1318 with folds 1330 that are substantially perpendicular to the broad sides 1322, 1324, and a second narrow side 1320 with folds 1330 that are substantially parallel to the broad sides 1322, 1324.

The one-piece flat tube 1410 illustrated in FIG. 21 has first and second narrow sides 1418, 1420 with multiple folds 1430 that are substantially parallel to the broad sides 1422, 1424 of the flat tube 1410. In other embodiments, the multiple folds 1430 of either or both narrow sides 1418, 1420 are instead substantially perpendicular to the broad sides 1422, 1424 of the flat tube 1410. Although each of the multiple folds 1430 at both of the narrow sides 1418, 1420 illustrated in FIG. 21 are substantially the same length, those of either or both narrow sides 1418, 1420 can instead be of different lengths L (e.g., see FIGS. 22 and 23). In such embodiments, the varying lengths of the narrow sides 1518, 1520, 1618 can take any of the forms described above in connection with the embodiment of FIG. 8, and can therefore produce any of the benefits also described therein. With reference to the embodiments of FIGS. 22 and 23, the illustrated arrangement of varying-length folds 1530, 1630 of the narrow sides 1518, 1520, 1630 (i.e., shorter folds 1530, 1630 flanked by longer folds 1530, 1630), can be generally effective in supporting temperature change loads. Also, sudden transitions in pressure from the narrow sides 1518, 1520, 1618 to the broad sides 1522, 1524, 1622, 1624 can be avoided with this arrangement. Additionally, as with the other one-piece flat tube embodiments described herein, one or more sets of multiple interior folds 1528 (such as the single set shown in FIG. 22) and/or a relatively high number of flow channels 1616 (such as those shown in FIG. 23) can be utilized to help support temperature change loads and to help withstand sudden transitions in pressure. Yet another measure aimed to improve temperature change load resistance is varying the distance “a” between folds to define increasingly wider flow channels 1516 toward the center of the flat tube 1510.

FIG. 24 shows an example of the manner in which any of the narrow side constructions shown in the two-piece flat tube embodiments of FIGS. 6-11, 14, and 15 can be employed in the narrow side of a one-piece flat tube having a continuous sheet of material as mentioned above. The narrow side 1718 shown in FIG. 24 is similar in many respects to that of FIG. 11 described above, with the exception of abutting adjacent folds 1730 and a single continuous sheet of material defining the folds 1730 rather than two overlapping sheets of material (or two overlapping portions of the same sheet of material). In this particular example, the distances “a” between the folds 1730 and the first interior fold 1728, and between the other interior folds 1728 are relatively small, and can range in some embodiments from 0.5 mm (0.019685 in) to 2 mm (0.07874 in) or more—even as large as 1 cm (2.54 in). Furthermore, in some embodiments, this flat tube 1610 has a width of about 42 mm (0.16535 in) allowing for multiple folds 1728 and flow channels 1716.

Flat tubes according to the some embodiments of the present invention can include an internal insert that reinforces at least one of the narrow sides of the flat tube while also potentially performing one or more other functions (e.g., reinforcing the broad sides of the tube, defining multiple flow channels in fluid communication or not in fluid communication with one another, defining flow turbulators, and the like). The insert can be defined by a separate portion of material that is connected to the sheet or sheets of material defining the exterior tube walls in the manufacture of the flat tubes, and can be used as a complement to or instead of interior folds as described in a number of the embodiments above. Examples of inserts have already been provided in connection with the illustrated embodiments of FIGS. 14 and 15.

Although inserts can be employed with one-piece flat tubes according to some embodiments of the present invention (described in greater detail below), a number of unique advantages are gained by the use of inserts in two-piece flat tubes. In some embodiments, such advantages are gained in the use of inserts in two-piece flat tubes constructed of sheet material having a relatively small thickness. In some embodiments, the wall material of the flat tubes has a thickness of no greater than about 0.20 mm (0.007874 in). However, in other embodiments, the inventors have discovered that a wall material of the flat tubes having a thickness of no greater than about 0.15 mm (0.0059055 in) provides significant performance results relating to the overall performance of the heat exchanger, manufacturability, and possible wall constructions (as disclosed herein) that are not possible using thicker wall materials. The relatively small wall material thickness can result in good thermal properties of the two-piece flat tubes having inserts. In some embodiments, a wall material thickness of such flat tubes of no less than about 0.050 mm (i.e., no less than about 0.0019685 in) provides good strength and corrosion resistance performance, whereas in other embodiments, a wall material thickness of such flat tubes of no less than about 0.030 mm (i.e., no less than about 0.00118 in) can be used. Also, the two-piece flat tubes having inserts described below can have dimensions similar to the two-piece flat tubes described above in connection with FIGS. 1-15.

As explained in greater detail below, the heat exchanger tubes and other portions of heat exchangers described herein can be manufactured using a number of manufacturing techniques and processes and can include corrosion protection features, such as, for example, those techniques and processes described below and illustrated in FIGS. 92-95. A number of manufacturing processes and techniques and the corrosion protection features referenced hereinafter are particularly advantageous when applied to heat exchanger tubes and portions of heat exchangers having significantly reduced material thickness. In addition, such techniques, processes, and corrosion protection features provide significant advantages relating to the overall performance of flat tubes and heat exchangers made from such material.

FIGS. 25-34 illustrate various two-piece flat tubes 1810, 1810A, 1910, 2010, 2110, 2210, 2310, 2410, 2510, 2610, 2710, 2810, 2910, 3010, 3110, 3210 each including a first portion 1812, 1812A, 1912, 2012, 2112, 2212, 2312, 2412, 2512, 2612, 2712, 2812, 2912, 3012, 3112, 3212, a second portion 1814, 1814A, 1914, 2014, 2114, 2214, 2314, 2414, 2514, 2614, 2714, 2814, 2914, 3014, 3114, 3214, and an insert 1834, 1834A, 1934, 2034, 2134, 2234, 2334, 2434, 2534, 2634, 2734, 2834, 2934, 3034, 3134, 3234, all of which can be constructed of sheets of material, such as strips of metal or other material. For ease of description, the following description refers only to the illustrated embodiment of FIGS. 25 and 26, it being understood that the following description applies equally to all of the embodiments illustrated in FIGS. 25-34 (barring inconsistent or incompatible description)

In some embodiments of the two-piece flat tube 1810 illustrated in FIGS. 25 and 26, the first and second portions 1812, 1814 and the insert 1834 can be constructed of a material (e.g., aluminum, aluminum alloy, or other material described herein) having a relatively low sheet thicknesses. For example, the inventors have discovered that a material thickness for these elements of no greater than about 0.15 mm (0.0098425 in) provides good performance results in many applications. In some embodiments, the material for these elements also has a thickness no less than about 0.03 mm (0.0011811 in). In many embodiments, it is preferred that a relatively smaller sheet thickness be used for the insert 1834 than for the first and second portions 1812, 1814 of the two-piece flat tube 1810. In spite of the relatively small sheet thicknesses, the narrow sides 1818, 1820 of the two-piece flat tube 1810 can have relatively improved stability, particularly when used in conjunction with features of the two-piece flat tube 1710 described below.

In the illustrated embodiment of FIGS. 25 and 26, each broad side 1822, 1824 of the flat tube 1810 is formed of a separate portion of material (such as a separate strip). The portions of material overlap in two locations to define two longitudinal seams 1844, 1846. These longitudinal seams 1844, 1846 of the two-piece flat tube 1810 extend from respective narrow sides 1818, 1820 of the flat tube 1810 to opposite broad sides 1822, 1824, in contrast to other illustrated embodiments (e.g., see FIG. 27 described in greater detail below), where the longitudinal seams extend from respective narrow sides of the flat tube to the same broad side of the flat tube. In the illustrated embodiment of FIGS. 25 and 26, the longitudinal seams 1844, 1846 are both located at and extend from a respective narrow side 1818, 1820 of the flat tube 1810 into the broad sides 1822, 1824 of the flat tube 1810. More specifically, the longitudinal seams 1844, 1846, namely those portions of the flat tube 1810 at which the sheet material of the flat tube 1810 is overlapped, extend about at least part of (and in some embodiments a majority or all of) the narrow sides 1818, 1820, and lie partially in a corresponding broad side 1822, 1824 of the flat tube 1810. The width of the seam 1844, 1846 can be determined according to desirable manufacturing purposes.

In some embodiments, the longitudinal seams 1844, 1846 of the flat tube 1810 present a flush or substantially flush outer surface of the flat tube 1810 (e.g., provide a substantially flat broad side 1822, 1824 of the flat tube 1810). For this purpose, that longitudinal edge of each longitudinal seam 1844, 1846 that is overlapped by the other longitudinal edge can be recessed by forming the overlapped longitudinal edge with an offset 1848, 1850. Accordingly, the longitudinal edge of one tube portion 1812, 1814 can be wrapped by and receive the corresponding longitudinal edge of the other tube portion 1814, 1812 in a recess 1848, 1850 to define the longitudinal seam 1844, 1846. Thus, for both seams 1844, 1846, the underlying longitudinal edge of the two overlapping tube portions 1812, 1814 can terminate within the interior of the flat tube 1810, and can be free prior to brazing, welding, or other securing techniques. As a result of this construction, flat tubes 1810 can be produced with precise desired widths (even without cutting or other machining operations, in some embodiments) despite the fact that looser tolerances are maintained for the widths of starting material for the individual tube portions 1812, 1814, since the overlapped longitudinal seams 1844, 1846 permit relative lateral positioning of the first and second tube portions 1812, 1814 in an assembled state. In particular, in some embodiments, a terminal longitudinal edge 1854, 1856 of each tube portion 1812, 1814 does not abut the other tube portion 1812, 1814, thereby permitting such adjustment.

The use of overlapping longitudinal seams such as those illustrated in the embodiment of FIGS. 25 and 26 provides significant reinforcement of the flat tube 1810 at the first and second narrow sides 1818, 1820—a feature that can be highly important in many applications where thermal stresses, temperature change loads, and failures due to pressure loading and debris impact are common in conventional flat tubes. In some embodiments, further reinforcement of the first and/or second narrow sides 1818, 1820 is provided by one or more folds of the first and/or second tube portions 1812, 1814 at the narrow sides 1818, 1820 (i.e., at the longitudinal edges of such portions 1812, 1814). Generally, folding the longitudinal edges of the first and/or second tube portions 1812, 1814 can increase the strength of the flat tube 1810 and resistance of the flat tube 1810 to damage. In those embodiments in which a narrow side 1818, 1820 is defined at least in part by overlapping longitudinal edges of the first and second tube portions 1812, 1814 (one extending about, receiving, or encompassing the other), either one or both of the overlapped longitudinal edges (e.g., the encompassed and encompassing edges) can be folded back to increase the thickness of that longitudinal edge at the narrow side 1818, 1820.

For example, it is envisioned that either or both overlapping longitudinal edges of tube portions 1812, 1814 at either or both narrow sides 1818, 1820 can include folds adjacent the corresponding gradation 1858, 1860 (described in greater detail below). For example, in some embodiments, the combined thickness of the first and second tube portions 1812, 1814 can be about 0.25 mm (0.0098425 in) or smaller in some embodiments, with either or both overlapping longitudinal edges having at least one fold to thicken the narrow side 1818, 1820, and with the material thickness of the insert 1834 being about 0.10 mm (0.003937 in) or less. In such embodiments, the thickness of the first and second tube portions 1818, 1820 can each be in the range of 0.05-0.15 mm (0.0019685-0.0059055 in), and can be in the range of 0.03-0.15 mm (0.0019685-0.0059055 in) in other embodiments.

It should also be noted that the overlapped longitudinal seam construction of the two-piece flat tube illustrated in FIGS. 25 and 26 can be employed in flat tube embodiments having no internal insert. For example, such a longitudinal seam construction can be employed in two-piece flat tubes having interior folds such as those described above in connection with the embodiments of FIGS. 1-13 and 16-24, or in other two-piece flat tubes.

Although not required, in many embodiments the tube portions (e.g., tube portions 1812, 1814 in FIGS. 25 and 26) have substantially the same shape, and can even be identical. When assembled as described above, the tube portions 1812, 1814 are arranged with their longitudinal edges reversed with respect to one another. For example, one longitudinal edge of one of the two tube portions 1812, 1814 includes a gradation 1856, 1860 defining a recess 48, 50 as described above, followed by a portion defining an arc 1862, 1864, while a corresponding overlapping longitudinal edge of the other tube portion 1814, 1812 includes a portion with a larger arc 1866, 1868 receiving the smaller arc 1862, 1864. Accordingly, in the illustrated embodiment of FIGS. 25 and 26, one smaller arc portion 1862, 1864 and one larger arc portion 1866, 1868 form one of the narrow sides 1818, 1820 as part of the manufacturing process of the two-piece flat tube 1810. It is to be understood that the term “arc” as used herein and in the appended claims is not restricted to a half round form. Moreover, the term “arc” as used herein and in the appended claims is inclusive of any suitable geometry for forming the narrow sides 1818, 1820, which can include square, triangular, or other open polygonal shapes, wave shapes, and other formations.

By employing tube portions that are substantially the same shape or identical, fewer part types (and in some cases, a single part type) can be used to construct the two-piece flat tube 1810, resulting in lower inventory, simpler assembly, and significant cost reductions.

The internal insert 1834 partially illustrated in FIG. 25 and fully illustrated in FIG. 26 is formed of a third piece of material, and generally includes two longitudinal edges 1838, 1840, either or both of which can lie substantially within a respective narrow side 1818, 1820 of the flat tube 1810. In some embodiments, the longitudinal edges 1838, 1840 are formed with a shape for this purpose, such that the longitudinal edges 1838, 1840 can be received within the interior shape of the narrow sides 1818, 1820. Also in some embodiments, at least part of either or both longitudinal edges 1838, 1840 have a shape corresponding to that of the narrow sides 1818, 1820. For example, either or both longitudinal edges 1838, 1840 can be formed into the shape of a loop 1842 such that at least part of the loop 1842 matches the shape of the corresponding narrow side 1818, 1820 of the flat tube 1810. In some embodiments, this shape correspondence can result in a reinforcement of the flat tube at the narrow sides 1818, 1820. Further reinforcement can be obtained by connecting either or both longitudinal edges 1838, 1840 with the narrow sides 1818, 1820, such as by brazing, welding, or in any other suitable manner.

With reference to FIG. 26, which illustrates the manner in which the two-piece flat tube 1810 can be assembled, the internal insert 1834 is shown received within arc portions 1862, 1864 of the first and second tube portions 1812, 1814 as the first and second tube portions 1812, 1814 are brought together during assembly. More particularly, the longitudinal edges 1838, 1840 of the internal insert 1834 are supported by the arc portions 1862, 1864 of the first and second tube portions 1812, 1814, and will be within the later-defined narrow sides 1818, 1820 of the tube 1810 to reinforce the narrow sides 1818, 1820 once assembly is complete. The resulting two-piece flat tube 1810 has narrow sides 1818, 1820 with a double wall thickness due to the overlapping longitudinal seams 1844, 1846 extending over and beyond the narrow sides 1818, 1820, and can also have further thickness defined by the that of the nested longitudinal edges 1838, 1840 of the internal insert 1834. In some cases, for example, the two-piece flat tube 1810 includes first and second tube portions 1812, 1814 collectively defining a wall thickness of about 0.20 mm (0.007874 in) to help prevent corrosion or deterioration, and/or to provide resistance against debris impact, and pressure and temperature change loads.

As explained in greater detail below, the heat exchanger tubes and other portions of heat exchangers described herein can be manufactured using a number of manufacturing techniques and processes and can include corrosion protection features, such as, for example, those techniques and processes described below and illustrated in FIGS. 92-95. A number of manufacturing processes and techniques and the corrosion protection features referenced hereinafter are particularly advantageous when applied to heat exchanger tubes and portions of heat exchangers having significantly reduced material thickness. In addition, such techniques, processes, and corrosion protection features provide significant advantages relating to the overall performance of flat tubes and heat exchangers made from such material.

The internal insert 1834 illustrated in the embodiment of FIGS. 25 and 26 has a number of corrugations 1852 across the width of the flat tube 1810. These corrugations 1852 can be joined to the interior of the broad sides 1822, 1824 of the first and second tube portions 1812, 1814 to form flow channels 1816 running in the longitudinal direction of the flat tube 1810. By using this arrangement, flow channels 1816 can be defined in the flat tube 1810 in a cost-effective manner, while also simplifying the manufacturing process of the two-piece flat tube 1810. In spite of the low wall thickness of the internal insert 1834 (which can be the same or smaller than the above-described thicknesses of the first and second tube portions 1812, 1814 described above), the flow channels 1816 formed within the two-piece flat tube 1810 can provide improved stability to internal pressure of the flat tube 1810.

The hydraulic diameter of the flow channels 1816 can be determined by appropriate design of the corrugations 1852 described above. In some embodiments, for example, the hydraulic diameter of the flow channels 1816 is relatively small considering that the small diameter d of the two-piece flat tube 1810 can be about 0.8 mm (0.031496 in), and that the number of corrugations 1852 can be relatively large.

In some embodiments, at least some of the corrugations 1852 are shaped to have one corrugation flank perpendicular or substantially perpendicular to the broad sides 1822, 1824 of the two-piece flat tube 1810, and an adjacent corrugation flank inclined with respect to the broad sides 1822, 1824 (e.g., see the center corrugations 1852 illustrated in FIG. 25, for example). In other embodiments, at least some of the corrugations 1852 are shaped to each have both corrugation flanks at a substantial incline with respect to the broad sides 1822, 1824 (e.g., see the left corrugations 1852 illustrated in FIG. 25, for example). In still other embodiments, at least some of the corrugations 1852 are shaped to have both flanks perpendicular or substantially perpendicular to the broad sides 1822, 1824 of the two-piece flat tube 1810.

An example of such an embodiment is shown in FIG. 33, which illustrates a two-piece flat tube 2210 that is substantially the same as that of FIGS. 25 and 26 with the exception of the insert shape. Like the embodiment of FIGS. 25 and 26, the insert 2234 illustrated in FIG. 33 reinforces the narrow sides 2218, 2220 by longitudinal edges 2238, 2240 of the insert 2234 lining at least a portion of the inner surface of each tube portion 2212, 2214 at the narrow sides 2218, 2220. In other embodiments, only one of the longitudinal edges 2238, 2240 of the insert 2234 extends into a corresponding narrow side 2218, 2220. It should be noted that the two-piece flat tube assembly shown in FIG. 33 can have any of the same features described herein in connection with the embodiment of FIGS. 25 and 26. In still other embodiments, at least some of the corrugations 1852 can define a curved wave pattern (e.g., sinusoidal), or any other profiled surface in which the corrugations are identical or different across the width of the two-piece flat tube 1810.

In some embodiments, the insert 1834 defines a number of flow channels 1816 having the same shape and size across the width of the two-piece flat tube 1810. In other embodiments, the insert 1834 can be shaped so that the shape and/or size of the flow channels 1816 varies across the width of the two-piece flat tube 1810 (e.g., by using an insert 1834 with different types of corrugations 1852 at different locations across the width of the two-piece flat tube 1810). An example of this is shown in FIG. 25, where both types of corrugations described above for the illustrated insert 1834 are used. In other embodiments, any number of different corrugation shapes and sizes can be used across the width of the two-piece flat tube 1810. This variance across the width can provide significant advantages over conventional flat tubes by adapting different portions of the flat tube 1810 for different flow and/or environmental conditions (e.g., different fluids or flow directions through different sections of the same flat tube 1810, different internal or external flow rates, temperatures, and/or pressures at different locations across the width of the flat tube 1810, and the like).

The internal insert 1834 illustrated in FIGS. 25 and 26 are formed of a single piece of material. However, it should be noted that in other embodiments, the internal insert 1834 can instead be formed of more than one part (in which case the flat tube assembly illustrated in FIGS. 25 and 26 can include four or more parts).

With continued reference to the embodiment of FIGS. 25 and 26, the thickness of at least one narrow side 1818, 1820 generally corresponds to the sum of the thicknesses of the two broad sides 1822, 1824 (and, more precisely, of the longitudinal edges of the first and second portions 1812, 1814) and the insert 1834. For example, the combined thickness of the overlapping longitudinal edges of the first and second portions 1812, 1814 and the insert 1834 can be about 0.25 mm (0.0098425 in) or less in some embodiments. It should also be noted that in some cases, each of the first and second tube portions 1812, 1814 and the insert 1834 can have substantially the same thickness (in any of the thickness ranges described above), such as in cases in which the same sheet material is used to construct all three pieces. In such cases, either or both narrow sides 1818, 1820 can be defined by a thickness that is approximately three times the material thickness of either first and second tube portion 1812, 1814 (i.e., when a loop 1842 on either or both longitudinal edges of the insert 1834 is received within a corresponding narrow side 1818, 1820 to increase the thickness thereof as described above). In some embodiments, either or both longitudinal edges of the insert 1834 can be folded over upon itself and then provided with a loop 1842 or otherwise shaped to at least partially correspond to the interior of the narrow side 1818, 1820, thereby reinforcing the wall material of the first and second portions 1812, 1814 at the narrow sides 1818, 1820. Any number of such longitudinal edge folds for the insert 1834 can be made to achieve a desired thickness, reinforcement, and stability of the narrow sides 1818, 1820.

In some embodiments having a narrow side reinforcing insert 1834 as described above, each of the first and second tube portions 1812, 1814 can have a thickness of less than 0.15 mm (0.00591 in), and the thickness of the insert 1834 can be no greater than about 0.10 mm (0.003937 in), such as a flat tube 1810 in which the first and second tube portions 1812, 1814 each have a thickness of about 0.12 mm (0.0047224 in), and in which the insert 1834 has a thickness of no greater than about 0.10 mm (0.003937 in). In other embodiments, the thickness of each of the first and second tube portions 1812, 1814 and the insert 1834 can be no less than about 0.05 mm (0.0019685 in) and no greater than about 0.15 mm (0.0059055) to provide a relatively cost-effective heat exchanger with good heat transfer and strength properties. In other embodiments, the thickness of each of the first and second tube portions 1812, 1814 and the insert 1834 can be no less than about 0.03 mm (0.00118 in) in other embodiments.

At least one of the first and second portions 1812, 1814 and the insert 1834 can have a brazing material coating on either or both sides thereof in order to permit such parts of the illustrated tube assembly to be joined by brazing. In the illustrated embodiment of FIGS. 25 and 26 by way of example only, the first and second portions 1812, 1814 and the insert 1834 of the flat tube 1810 is manufactured from aluminum or aluminum alloy sheeting made available in endless strips of material coated on at least one side with brazing material.

As shown in FIGS. 25 and 26, the two-piece flat tube 1810 of the illustrated embodiment defines a small diameter d and a large diameter D. Using the wall thicknesses described earlier, the inventors have discovered that a small diameter d of at least about 0.7 mm (0.027559 in) provides good performance results in many applications, such as in radiators. Also using the wall thicknesses described earlier, the inventors have discovered that a small diameter d of no greater than about 1.5 mm (approx. 0.059055 in) provides good performance results in many applications, such as in radiators. In the case of charge air coolers and other applications, the inventors have discovered that the small diameter d can be larger than about 1 cm (0.3937 in) to provide good performance results. Although such small diameter dimensions can be employed in various embodiments, any of the small diameter dimensions described above with regard to all of the flat tube embodiments disclosed herein can be used. The large diameter D of the two-piece flat tube 1810 illustrated in FIGS. 25 and 26 can have any size desired (including those also described above with regard to all of the flat tube embodiments disclosed herein), based at least in part upon the width of the starting material used to construct the flat tube 1810.

As mentioned above, in some embodiments, either or both longitudinal edges of the insert 1834 can be provided with any number of folds to achieve a desired thickness for increased reinforcement and stability of the first and second portions 1812, 1814 at the narrow sides 1818, 1820. An example of such an embodiment is illustrated in FIGS. 28 and 29. The two-piece flat tube 1910 illustrated in FIGS. 28 and 29 is substantially the same as that of FIGS. 25 and 26 with the exception of the insert shape.

FIG. 28 illustrates the flat tube 1910 with a narrow side 1918 at a stage in which the large arc portion 1968 has not been completely manufactured. In other words, one longitudinal edge of the second tube portion 1914 is not wrapped around the already-formed smaller arc portion 1962 formed by a corresponding longitudinal edge of the first tube portion 1912. This longitudinal edge of the second tube portion 1914 is displaced or moved around the smaller arc portion 1962 to complete the narrow side 1918. As a consequence, the resulting longitudinal seam 1944 lies in one broad side 1922, with another of the two longitudinal seams 1946 lying in the other broad side 1924. These longitudinal seams 1944, 1946 are located at the narrow sides 1918, 1920 of the two-piece flat tube 1910 as described in earlier embodiments.

In the illustrated embodiment of FIGS. 28 and 29, the longitudinal edges 1938, 1940 of the insert 1934 have been folded several times, as best shown in FIG. 29. The longitudinal edges 1938 with these folds 1970 are received within the narrow sides 1918, 1920 of the two-piece flat tube 1910, and can provide significant reinforcement to the overlapped longitudinal edges of the first and second tube portions 1912, 1914 at the narrow sides 1918, 1920. In other embodiments, only one of the longitudinal edges 1938, 1940 of the insert 1934 has such folds 1970.

The number of folds 1970 of the longitudinal edges 1938, 1940 can depend at least in part upon the dimensions of the flat tube 1910. In some embodiments by way of example only, the two-piece flat tube 1910 has a small diameter d of about 1.0 mm (0.03937 in), the first and second tube portions 1912, 1914 each have a material thickness of about 0.15 mm (0.0059055 in), and the material thickness of the insert 1934 is about 0.05 mm (0.0019685 in), wherein about 10 folds are created on each longitudinal edge 1938, 1940 of the insert 1934. Although these multiple folds 1970 can have varying lengths, in some embodiments the maximum length L of these folds is about 1.0 mm (0.03937 in). Also, these multiple folds 1970 can run in a direction parallel or substantially parallel to the broad sides 1922, 1924 of the two-piece flat tube 1910 in some embodiments (see FIGS. 28 and 29), and can run in other directions (e.g., perpendicular to the broad sides 1922, 1924) in other embodiments. It is to be understood that the wall thicknesses of the first and second tube portions 1912, 1914 and the insert 1934 can vary, as can the distances d and L based upon desired specifications of the flat tube 1910.

It should be noted that the two-piece flat tube assembly shown in FIGS. 28 and 29 can have any of the same features described herein in connection with the embodiment of FIGS. 25 and 26.

FIG. 27 illustrates a two-piece flat tube according to an additional embodiment of the present invention. This embodiment employs much of the same structure and has many of the same properties as the embodiments of the flat tube described above in connection with FIGS. 25, 26, 28, 29 and 33. Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiments described above in connection with FIGS. 25, 26, 28, 29 and 33. Reference should be made to the description above in connection with FIGS. 25, 26, 28, 29 and 33 for additional information regarding the structure and features, and possible alternatives to the structure and features of the two-piece flat tube illustrated in FIG. 27 and described below. Structure and features of the embodiment shown in FIG. 27 that correspond to structure and features of the embodiments of FIGS. 25, 26, 28, 29 and 33 are designated hereinafter in the 1800 series of reference numbers.

Like the embodiments of the present invention described in connection with FIGS. 25 and 26, the tube assembly illustrated in FIG. 27 has first and second portions 1812A, 1814A and an insert 1834A. The opposite longitudinal edges 1838A, 1840A of the insert 1834A line the inner surfaces of both pairs of overlapped longitudinal sides of the first and second tube portions 1812A, 1814A, thereby reinforcing the narrow sides 1818A, 1820A of the flat tube 1810A.

The two-piece flat tube 1810A illustrated in FIG. 27 is an example of the manner in which both longitudinal seams 1844A, 1846A joining the first and second portions 1812A, 1814A of the flat tube 1810A can extend to and on the same broad side 1822A, 1824A of the flat tube 1810A. In the illustrated embodiment of FIG. 27, both longitudinal seams 1844A, 1846A extend to and on the second broad side 1824A of the flat tube 1810A. Alternatively, the longitudinal seams 1844A, 1846A can be formed in the first broad side 1822A, if desired. In the illustrated embodiment, the second broad side 1824A defined primarily by the second tube portion 1814A is capable of absorbing relatively loose tolerances (i.e., is capable of tolerance equalization) at its opposite longitudinal edges. However, in some embodiments, the first broad side 1822A defined primarily by the first tube portion 1812A does not have the same capability or degree of capability, because each of its longitudinal edges can lie against or immediately adjacent a gradation 1858A, 1860A of the second tube portion 1814A.

With continued reference to the illustrated embodiment of FIG. 27, the longitudinal seams 1844A, 1846A extend from respective narrow sides 1818A, 1820A in directions toward the center of the flat tube 1810A. A significant portion of each longitudinal seam 1818A, 1820A (i.e., the gradations 1858A, 1860A), however, lies in the same broad side 1824A, where the cross-sectional length e of each gradation 1858A, 1860A measured to the distal edge of the narrow sides 1818A, 1820A can be determined according to the desired manufacturing process used to produce the tube portions 1812A, 1814A. In the illustrated embodiment of FIG. 27, the small diameter d of the two-piece flat tube 1810A is in the range of about 0.7-1.5 mm (0.027559-0.059055 in) when the two-piece flat tube 1810A is incorporated in a radiator, although other small diameters d are possible for the same and different applications, including the diameters d described above in connection with the embodiment of FIGS. 25 and 26, and those described above in connection with the small and large diameters for all of the flat tubes of the present invention disclosed herein. For example, in other constructions, the small diameter d of the flat tube 1810A can be greater than 1.0 cm (approx. 0.3937 in).

As with the other two-piece flat tube embodiments described herein, it is envisioned that a manufacturing process of the flat tube 1910 includes at least partially forming the two tube portions 1912, 1914 from respective strips of sheet material, and then joining the at least partially formed strips to one another as described herein by the end of the manufacturing line.

FIGS. 30-32 illustrate two additional constructions of flat tubes according to additional embodiments of the present invention. These embodiments employ much of the same structure and have many of the same properties as the embodiments of the flat tube described above in connection with FIGS. 25-29 and 33. Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiments described above in connection with FIGS. 25-29 and 33. Reference should be made to the description above in connection with FIGS. 25-29 and 33 for additional information regarding the structure and features, and possible alternatives to the structure and features of the flat tubes illustrated in FIGS. 30-32 and described below. Structure and features of the embodiments shown in FIGS. 30-31 and 32 that correspond to structure and features of the embodiments of FIGS. 25-29 and 33 are designated hereinafter in the 2000 and 2100 series of reference numbers, respectively.

The tube assembly illustrated in FIGS. 30 and 31 is substantially the same as that shown in FIG. 27, with the exception of the insert shape. In particular, the tube assembly illustrated in FIGS. 30 and 31 is an example of the manner in which the insert 2034 can take different shapes to define flow channels 2016 of different shapes and sizes. By way of example, the illustrated internal insert 2034 includes corrugations 2052 having flanks that are substantially perpendicular to the broad sides 2022, 2024 of the two-piece flat tube 2010. The corrugation flanks are joined together by substantially flat sections that can be brazed, welded, or secured in any other suitable manner to the inside surfaces of the broad sides 2022, 2024 of the first and second tube portions 2012, 2014. This particular construction of lamellae or internal insert 2034 is generally referred to as flat-top lamellae.

With continued reference to FIGS. 30 and 31, the longitudinal edges 2038, 2042 of the internal insert 2034 are shaped to each include a gradation 2072 and a connecting arc 2074 received substantially within and reinforcing the narrow sides 2018, 2020 of the two-piece flat tube 2010. In other embodiments, only one of the longitudinal edges 2038, 2042 is provided with these features.

In any of the insert embodiments described herein, the inserts can be provided with features that increase or sustain turbulence within the flow channels defined at least in part by the inserts. An example of such features is shown in FIGS. 32A and 32B. In this embodiment, the flanks and flat sections of the corrugations 2152 in the illustrated insert 2134 include winglets 2176 (not shown in FIG. 32A) positioned to increase or sustain flow turbulence within the flow channels 2116. The winglets 2176 can be arranged or distributed at intervals along the length of the flat tube 2110 in any patterned or patternless manner, and can be located in any feature or combination of features of the corrugations 2152. Also, it should be noted that the winglets 2176 can include shapes other than those shown in FIGS. 32A and 32B.

The flat tube assembly illustrated in FIGS. 32A and 32B also provides an example of how either or both longitudinal edges of an insert in any of the embodiments herein need not necessarily be received or otherwise located within the overlapped longitudinal edges of the first and second tube portions, and need not necessarily be part of or extend to the narrow sides of the flat tube. In the particular construction shown in FIGS. 32A and 32B by way of example, the internal insert 2134 includes at least one longitudinal edge 2140 that ends before the narrow side 2120. Instead, the longitudinal edge 2140 is adjacent one of the broad sides 2124. Other constructions of the insert 2124 can include either or both longitudinal edges 2138, 2140 adjacent the other broad side 2122 of the flat tube 2110, either or both rolled longitudinal edge 2138, 2140 not within or nested in a corresponding narrow side 2118, 2120 of the flat tube 2110, and the like.

FIG. 34 illustrates ten constructions of flat tubes according to additional embodiments of the present invention. These embodiments employ much of the same structure and have many of the same properties as the embodiments of the flat tube described above in connection with FIGS. 25-33. Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiments described above in connection with FIGS. 25-33. Reference should be made to the description above in connection with FIGS. 25-33 for additional information regarding the structure and features, and possible alternatives to the structure and features of the flat tubes illustrated in FIG. 34 and described below. Structure and features of the embodiments shown in FIG. 34 that correspond to structure and features of the embodiments of FIGS. 25-33 are designated hereinafter in respective series of reference numbers beginning with 2300.

As described above in connection with the illustrated embodiment of FIGS. 25 and 26, further reinforcement of the first and/or second narrow sides of a flat tube can be provided by one or more folds of the first and/or second tube portions at the narrow sides (i.e., at the longitudinal edges of such portions). Generally, folding the longitudinal edges of the first and/or second tube portions can increase the strength of the flat tube and resistance of the flat tube to damage. This feature can be employed in any of the embodiments described in connection with FIGS. 25-33. Examples of flat tubes having longitudinal folded edges are illustrated in FIG. 34, wherein inserts defining generally rectangular flow channels and not extending into or folded within the folds of the narrow tube sides are illustrated by way of example only. Any of the other types of inserts (or no inserts at all) or longitudinal insert construction and position described herein can instead be used as desired.

Each of the flat tubes 2310, 2410, 2510, 2610, 2710, 2810, 2910, 3010, 3110, 3210 illustrated in FIG. 34 includes at least one longitudinal edge of at least one of the first and second tube portions 2312, 2412, 2512, 2612, 2712, 2812, 2912, 3012, 3112, 3212 and 2314, 2414, 2514, 2614, 2714, 2814, 2914, 3014, 3114, 3214 having a fold 2330, 2430, 2530, 2630, 2730, 2830, 2930, 3030, 3130, 3230. Each of the constructions illustrated in FIG. 34 have an encompassed edge 2380, 2382 . . . 3280, 3282 (that is, the longitudinal edge 2380, 2382 . . . 3280, 3282 that is at least partially surrounded by a longitudinal edge 2378, 2384 . . . 3278, 3284 of the other tube portion 2312, 2314 . . . 3212, 3214) with at least one fold 2330 . . . 3230. Some of the constructions in FIG. 34 illustrate an encompassing edge 2978, 2984, 3078, 3074, 3178, 3174, 3278, 3274 (that is, the longitudinal edge 2978, 2984, 3078, 3074, 3178, 3174, 3278, 3274 that at least partially surrounds a longitudinal edge 2980, 2982, 3080, 3082, 3180, 3182, 3280, 3282 of the other tube portion 2912, 2914, 3012, 3014, 3112, 3114, 3212, 3214) with at least one fold 2930, 3030, 3130, 3230. Although the opposite narrow ends of each two-piece flat tube illustrated in FIG. 34 employ the same folded construction, in other embodiments (with or without inserts) only one of the two narrow ends has such a construction, in which case the other narrow end can have any of the other folded constructions described herein or has no longitudinal folded tube edge portions at all. In other embodiments, each of the longitudinal edges of at least one of the narrow ends of the two-piece flat tube (with or without an insert) has at least one fold.

In some embodiments, one of the narrow ends of any of the flat tubes illustrated in FIG. 34 can have any of the longitudinal folded edge constructions described and/or illustrated herein, while the other narrow end can have any of the folded constructions described above and/or illustrated in connection with any of the embodiments shown in FIGS. 1-24 (with or without inserts). In such cases, the other narrow end can be defined by a folded continuous sheet of material as described in detail above in connection with the one-piece tube embodiments of FIGS. 16-22, thereby resulting in a one-piece tube.

The combination of the longitudinal folded constructions of the first and second tube portions described herein with the relatively small thickness dimensions of the material that can be employed in some embodiments (as described above) can produce flat tubes having a significantly reduced weight without compromise of strength and stability.

For ease of description, the constructions of the flat tubes 2310 . . . 3210 illustrated in FIG. 34 include a similar configuration as the flat tube 1810 shown in FIGS. 25 and 26 with respect to the orientation of the first and second portions 2312, 2314 . . . 3212, 3214, and are classified into three groups: B, C, and D. Each of the groups B, C, and D illustrates alternative characteristics of the flat tube 2310 . . . 3210. As mentioned above, it is to be understood that the features illustrated in FIG. 34 are also applicable to other configurations of two-piece and one-piece flat tubes described and/or illustrated herein, and can be utilized with or without an insert. The flat tubes 2310, 2410, 2510, 2610, 2710, 2810 of Groups B and C each include a non-folded encompassing longitudinal edge 2378, 2384, 2478, 2484, 2578, 2584, 2678, 2684, 2778, 2784, 2878, 2884 of the first and second tube portions 2312, 2314, 2412, 2414, 2512, 2514, 2612, 2614, 2712, 2714, 2812, 2814 respectively. More specifically, the encompassing edges 2378, 2384, 2478, 2484, 2578, 2584, 2678, 2684, 2778, 2784, 2878, 2884 at least partially enclose encompassed edges 2382, 2380, 2482, 2480, 2582, 2580, 2682, 2680, 2782, 2780, 2882, 2880 having at least one fold 2330, 2430, 2530, 2630, 2730, 2830. The folds 2330, 2430, 2530, 2630, 2730, 2830 of the encompassed edges 2382, 2380, 2482, 2480, 2582, 2580, 2682, 2680, 2782, 2780, 2882, 2880 can be substantially parallel to the broad sides 2322, 2324, 2422, 2424, 2522, 2524, 2622, 2624, 2722, 2724, 2822, 2824 (e.g., Groups B and C). Also, the folds 2330, 2430, 2530 can include a portion parallel to the encompassing edge 2378, 2384, 2478, 2484, 2578, 2584 (e.g., Group B).

The flat tubes 2910, 3010, 3110 of Group D include narrow sides 2918, 2920, 3018, 3020, 3118, 3120, wherein both the encompassing edges 2978, 2984, 3078, 3084, 3178, 3184 and the encompassed edges 2982, 2980, 3082, 3080, 3182, 3180 of the first and second tube portions 2912, 2914, 3012, 3014, 3112, 3114 have folds 2930, 3030, 3130. As a result, the stability of the narrow sides 2918, 2920, 3018, 3020, 3118, 3120 can be increased with respect to the narrow sides 2318, 2320, 2418, 2420, 2518, 2520, 2618, 2620, 2718, 2720, 2818, 2820 of the flat tubes 2310, 2410, 2510, 2610, 2710, 2810 in Groups B and C. Furthermore, the encompassed and encompassing edges 2982, 2980, 3082, 3080, 3182, 3180 and 2978, 2984, 3078, 3084, 3178, 3184 of each of the flat tubes 2910, 3010, 3110 in Group D define only one fold 2930, 3030, 3130 (although more folds are possible in other embodiments), whereas the encompassed edges 2382, 2380, 2482, 2480, 2582, 2580, 2682, 2680, 2782, 2780, 2882, 2880 of the Group B and C flat tubes 2310, 2410, 2510, 2610, 2710, 2810 define more than one fold 2330, 2430, 2530, 2630, 2730, 2830. Also with reference to the Group D flat tubes 2910, 3010, 3110, the one fold 2930, 3030, 3130 of each encompassing edge 2978, 2984, 3078, 3084, 3178, 3184 is substantially parallel to the outermost portion of the flat tube 2910, 3010, 3110, and at least a portion of the fold 2930, 3030, 3130 of each encompassed edge 2982, 2980, 3082, 3080, 3182, 3180 is substantially parallel to the broad sides 2922, 2924, 3022, 3024, 3122, 3124 of the flat tubes 2910, 3010, 3110.

With continued reference to the various flat tube embodiments illustrated in FIG. 34, it is to be understood that the number of folds 2330 . . . 3230 at the encompassing and encompassed edges 2382, 2380 . . . 3282, 3280 and 2378, 2384 . . . 3278, 3284, and the design or shape of the folds 2330 . . . 3230 can be adjusted according to a desired set of parameters. Furthermore, although the internal insert 2334 . . . 3234 of the flat tube embodiments illustrated in FIG. 34 is not used for reinforcing the narrow sides 2318, 2320 . . . 3218, 3220, in other embodiments, either or both longitudinal edges 2338, 2340 . . . 3238, 3240 of the insert 2334 . . . 3234 is folded with and within the longitudinal edges 2382, 2380 . . . 3282, 3280 and 2378, 2384 . . . 3278, 3284 of the first and second tube portions 2312, 2314 . . . 3212, 3214. Yet other constructions of the flat tube can include forming folds with the longitudinal edges of a one-piece strip as mentioned above.

same features and are connected to the flat tube 4410 in substantially the same way as described below and illustrated in FIGS. 70, 70A, 71, 76, and 77.

The collection tank 4467 can be constructed from any number of different parts. For example, the collection tank 4467 illustrated in FIGS. 70, 70A, 71, 76, and 77 is formed as a single unitary body, such as by injection molding or another suitable process. In this and other embodiments, at least one row of receiving openings 4479 (described in greater detail below) is integrally formed with the collection tank 4467. In other constructions, such as the collection tank embodiment illustrated in FIGS. 72-75 and described below, the collection tank is formed from two or more separate pieces by injection molding or any other suitable manner and connected together, and having at least one row of receiving openings in one or more of the pieces. In such embodiments for example, the collection tank 4467 can have one or more walls in which the receiving openings 4479 are defined, and one or more other walls defined by separate parts of the collection tank 4467, such that the other walls can be assembled at a stage later than that in which flat tubes 4410 are received within the receiving openings 4479.

The illustrated collection tank 4467 includes a series of receiving openings 4479 along a surface thereof. Each receiving opening 4479 is surrounded by a wall integrally formed with at least a portion of the collection tank 4467 and shaped to receive a corresponding free end 4477 of a flat tube 4410. The flat tubes 4410 can take any of the forms described herein, and can be cut to length specified by the desired parameters of the flat tube 4410 or corresponding application. With reference to FIGS. 70, 7A, and 71, part of the process of manufacturing a heat exchanger 4463 includes setting free ends 4477 of flat tubes 4410 (according to any of the embodiments described herein) into receiving openings 4479 of the collection tank 4467. In some embodiments, this process can be performed by pushing the collection tank 4467 onto the free flat tube ends 4477 in a manner similar to that shown schematically in FIG. 62. Alternatively, the free ends 4477 of the flat tubes 4410 can be pushed into the receiving openings 4479, or the flat tubes 4410 and the collection tank 4467 can be moved toward one another and pushed together to establish these connections.

In some embodiments, the flat tubes 4410 connected to the collection tank 4467 can have one or more sets of fins 4459 (see FIG. 77) according to any of the embodiments described herein. By way of example only, finned tubes 4461 already assembled and brazed in upstream manufacturing steps (such as any of those described above) can have fins 4559 with wall thicknesses of about 0.030-0.090 mm (0.0011811-0.0035423 in.), and can subsequently be secured to a collection tank 4467. For example, protruding free ends 4477 of individual flat tubes 4410 with fins 4459 already brazed thereto or of such finned tubes 4461 already assembled and brazed into a block or core 4465 can remain free during brazing (e.g., while in a brazing furnace), and therefore have no fins 4559 to interfere with their later insertion into receiving openings 4479 of a collection tank 4467. Both ends of the flat tubes 4410 in any such embodiment can protrude and be free as just described for connection to opposite collection tanks 4467.

In those embodiments in which the core 4465 is connected as just described, the core 4465 can be formed from flat tubes 4410 and fins sets 4459 by alternate stacking of the flat tubes 4410 and fins sets 4459. An example of such a core construction is illustrated in FIG. 77, which shows a brazed flat tube-fin core 4465 having two collection tanks 4467 each with a port for connection to other equipment, wherein cooling air flows through the fins 4459 to cool fluid within the flat tubes 4410. The heat exchanger 4463 illustrated in FIG. 77 is only one of many types of possible heat exchangers to which one of more of the collection tanks 4467 can be connected. By way of example only, either of the illustrated collection tanks 4467 can be a reversing tank, such that both inlet and outlet ports are arranged on the same collection tank 4467.

The flat tubes 4410 (with or without fins connected thereto as described in earlier embodiments above) can be individually inserted into respective receiving openings 4479 of a collection tank 4467. However, significant advantages can be achieved by inserting two or more of the flat tubes 4410, and in some cases all of the flat tubes 4410 of a core 4465, into their respective receiving openings 4479 at the same or substantially the same time, such as in a single step. This process can be performed when two or more of the flat tubes are 4410 are already connected together, such as by a brazing or other attachment processes (including those described herein) to define an entire flat tube heat exchanger core 4465 or portion thereof. Such a process can make possible the use of a larger number of collection tank materials. However, depending at least in part upon the material used for the collection tank 4467 and the process used to secure the fins 4459 to the flat tubes 4410, in some embodiments it is desirable to introduce the free ends 4477 of the flat tubes 4410 into respective receiving openings 4479 of the collection tank 4467 subsequent to post-brazing cooling of the tube-fin core 4465.

Many heat exchanger manufacturing processes require the exposure of the tubes and the collection tank to elevated temperatures for soldering, welding, brazing, and other attachment processes, such as receiving the flat tubes and the collection tank in a furnace or other heated environment to join the flat tubes to the collection tank. Such processes therefore prevent the use of many collection tank materials—at least those materials used for the parts of collection tanks defining the connection locations for the flat tubes (e.g., the collection tank wall or walls defining the receiving openings). Therefore, these parts of collection tanks are typically comprise metal. By connecting the collection tank to two or more flat tubes that have already been soldered, welded, brazed, or otherwise already joined together as described above, plastic or other lower temperature materials can be used for many parts, all, or substantially all of the collection tank 4467. For example, the part or parts of the collection tank 4467 defining the receiving openings 4479 can comprise plastic. The entire collection tank 4467 in the illustrated embodiment of FIGS. 70, 70A, 71, 76, and 77 is manufactured from a plastic material, although other materials can be used in other embodiments. In those embodiments in which part or all of the collection tank 4467 comprises plastic, such parts can be manufactured by injection-molding, for example.

With reference again to FIGS. 70 and 71, the receiving openings 4479 of the collection tank 4467 shown therein have curved surfaces 4481 to aid insertion of the flat tube ends 4477. In other embodiments, other shapes (e.g., flat inclined surfaces, perpendicular corner surfaces, and the like) are used instead.

When fully inserted into their respective receiving openings 4479, the flat tube ends 4477 reach to respective locations below the inner surface 4483 of the collection tank 4467, as best shown in FIG. 71, thereby preventing an undesirable pressure drop created by the flat tube ends 4477 during operation of the heat exchanger 4463.

In the illustrated embodiment of FIGS. 70, 70A, 71, 76, and 77, the receiving openings 4479 of the collection tank 4467 are shaped to define a rear portion 4485 (with reference to the direction of flat tube insertion in FIGS. 70, 70A, 71, 76, and 77) that is substantially the same as the cross-sectional shape of the flat tube ends 4477. Although the rear portion 4485 of each receiving opening 4479 can be dimensioned to define a clearance fit with a flat tube end 4477, in other embodiments (such as that shown in FIGS. 70, 70A, 71, 76, and 77) an interference fit is used. In those embodiments in which an interference fit is employed, a slight pressure can be exerted upon the collection tank 4467 and/or on the flat tube 4410 to fully insert the flat tube end 4477 into the rear portion 4485 of the receiving opening 4479, thereby providing a seal between the collection tank 4467 and the flat tube end 4477 that can be fluid tight or substantially fluid tight.

In some embodiments, a feature of the collection tank 4467 and/or of the flat tube ends 4477 is used to control or limit the amount of insertion of the flat tube ends 4477 into the receiving openings 4479. For example, a stop (not shown in FIGS. 70, 70A, 71, 76, and 77, but visible in FIG. 80, indicated by reference numeral 4675) can be formed on the flat tube end 4477 and/or on the inside surface of the receiving opening 4479 to limit the depth of insertion of the flat tube end 4477.

In other embodiments, one or more of flat tube ends 4477 can extend through a corresponding receiving opening 4479 and into an interior chamber 4487 of the collection tank 4467. In such embodiments, the flat tube end 4477 can be deformed in any manner, such as by being bent over the surfaces of the interior chamber walls 4483 adjacent the receiving opening 4479 to at least partially match the shape of such surfaces.

In the illustrated embodiment of FIGS. 70, 70A, 71, 76, and 77, adhesive 4489 is used to secure the flat tube ends 4477 within the receiving openings 4479 (see FIG. 71) of the collection tank 4467. A number of different adhesives can be used, including those that harden immediately or over time, and those that retain a degree of flexibility after setting. For example, silicone adhesives produced by Dow Corning® can be used in many embodiments. In some embodiments, the adhesive 4489 insures a permanent and tight joint between the flat tube ends 4477 and the interior surfaces of the receiving openings 4479.

The adhesive 4489 can further function as a sealant to prevent loss of fluid from the collection tank 4467. In other embodiments, the flat tube ends 4477 are sufficiently secured within the receiving openings 4479 by their insertion in the rear portions 4485 of the receiving openings 4479, in which cases sealant having no or substantially no adhesive properties can be used in place of adhesive 4489. For ease of description, the term “adhesive” with reference to the flat tube-to-collection tank connections refers to adhesive that may or may not function as a sealant, it being understood that in other embodiments such material can instead function only or primarily as a sealant.

As best shown in FIG. 71, the adhesive 4489 can substantially cover a significant portion of the flat tube end 4477, and in some embodiments surrounds the entire periphery of the flat tube end 4477 in at least one location along the length thereof. In the illustrated embodiment of FIGS. 70, 70A, 71, 76, and 77, a terminal portion of the flat tube end 4477 is not covered with adhesive 4489 due to its location within the rear portion 4485 of the of the receiving opening 4479. By virtue of the relatively close fit between the rear portions 4485 of the receiving openings 4479 and the flat tube ends 4477 as described above, fluid passing through the collection tank 4467 (e.g., liquid coolant or other fluid used as a heat exchange medium) can be prevented from coming into contact with the adhesive 4489.

Adhesive 4489 can be introduced between the flat tube ends 4477 and the interior surfaces of the receiving openings 4479 in a number of different manners according to various embodiments of the present invention, many of which include the introduction of adhesive 4489 after or while the flat tube ends 4477 are received within their respective receiving openings 4479. Before further description of such embodiments, however, it should be noted that adhesive 4489 can be applied to the interior of the receiving openings 4479 and/or to the exterior of the flat tube ends 4477 in any manner (e.g., spray, roller, or other applicator, and the like) prior to insertion of the flat tube ends 4477 within the receiving openings 4479.

Introduction of adhesive 4489 between the flat tube ends 4477 and interior surfaces of the receiving openings 4479 during or after tube end insertion can provide greater control over the amount and/or resulting locations of adhesive 4489 in the finished heat exchanger 4463, and can result in more reliable connection and/or seals between the flat tube ends 4477 and the collection tank 4467.

In order to provide space for adhesive 4489 to be introduced between the flat tube ends 4477 and the interior surfaces of the receiving openings 4479, the receiving openings 4479 and/or flat tube ends 4477 can be shaped to define one or more gaps 4493 therebetween. For ease of description, the term “gap” (when used herein to refer to the space where adhesive 4489 is received as described herein) refers to one or more of such gaps, regardless of particular peripheral location about a flat tube end 4477 and regardless of whether two or more of such gaps for the same flat tube end 4477 are in fluid communication with one another.

In some embodiments, the gap 4493 between the flat tube end 4477 and the adjacent interior surface defining the receiving opening 4479 can have a width of at least about 0.3 mm (0.011811 in) to permit proper adhesive injection (described below). Also, through experimentation, the inventors have discovered that this gap width of no greater than about 1.0 mm (0.03937 in) provides good performance results. A number of considerations can at least partially define the size of the gap 4493, such as the amount of adhesive needed, characteristics of the adhesive (e.g., viscosity and set time), and limitations on the distance between adjacent flat tubes 4410. Another consideration relates to the need in some embodiments for the collection tank 4467 to have a thickness or depth that is minimized. For example, in some embodiments the collection tank 4467 overhangs the flat tube core 4465 by a minimum amount in order to reduce the amount of space wasted by the heat exchanger 4463 within a vehicle.

In some constructions, the collection tanks 4467 have substantially no overhang in the direction of the depth of the tube-fin core 4465 to avoid waste of the available space required for installation of a heat exchanger 4463 into a vehicle. For example, in the illustrated embodiment of FIGS. 70, 70A, 71, 76, and 77, and with particular reference to FIG. 76, an undeformed flat tube end 4477 requires a minimum or substantially no overhang of the collection tank 4467 past the flat tube-fin core 4465, which addresses the need for a reduced space requirement of the heat exchanger 4463. In some embodiments, the overhang can also be reduced (e.g., on the order of a few millimeters) when the manufacturing process of the heat exchanger 4463 includes the use of deformed flat tube ends 4477 (described below).

In some embodiments, the adhesive 4489 is introduced by injection through one or more openings in the collection tank 4467 or through one or more gaps between the flat tube ends 4477 and the collection tank 4467 accessible from the exterior of the collection tank 4467 and flat tubes 4410 once these parts are at least partially assembled. For example, the collection tank 4467 illustrated in FIGS. 70, 70A, 71, 76, and 77 has a number of injection openings 4491, each extending through a wall 4495 of the collection tank 4467 to a gap 4493 defined between the flat tube end 4477 and one or more walls defining the receiving opening 4479.

Such injection openings 4491 can be located on either or both longitudinal sides of the collection tank 4467. Also, more than one injection opening 4491 can extend to the same receiving opening 4479. In such cases, adhesive 4489 can be injected simultaneously to the same receiving opening 4479, such as through two injection openings 4491 on opposite longitudinal sides of the collection tank 4467. Adhesive can be injected into the gap 4493 corresponding to each flat tube 4410 one at a time, in banks of gaps 4493 (corresponding to respective flat tubes 4410) at the same time or substantially the same time, or in all of the gaps 4493 of a core 4465 at the same time or substantially the same time. In some embodiments, the adhesive 4489 coats the entire periphery of each flat tube end 4477, and/or can fill the gap 4493 between the flat tube end 4477 and the adjacent walls defining the receiving opening 4479. Also, in some embodiments (e.g., that of FIGS. 70, 70A, 71, 76, and 77) the terminal ends of the flat tubes 4410 can be left uncoated with adhesive 4489.

An alternative manner in which to introduce adhesive between a flat tube end 4477 and interior walls of the receiving openings 4479 is to inject adhesive through a bottom opening or gap 4497 between these parts and in fluid communication with the gap 4493 described above. This type of adhesive introduction can be used in addition to or in place of injection through injection openings 4491 as also described above, and can eliminate the need for the injection openings 4491.

FIG. 84 is a block diagram describing a manufacturing process of a heat exchanger 4463 according to an embodiment of the present invention, and referencing stations or steps of manufacturing, and is accompanied by a schematic view of a heat exchanger 4463 manufacturing by this process. The term “station” is used herein only for ease of description, and does not alone indicate or imply that there is a physical separation between such “stations” in a manufacturing line. For example, the collection tanks 4467 can be placed on the free flat tube ends 4477 (Station III) at the same or different location as the process of applying the adhesive 4489 (Station IV).

FIG. 72-75 illustrate a collection tank 4467 according to an additional embodiment of the present invention. This embodiment employs much of the same structure and has many of the same properties as the embodiments of the collection tank 4467 described above in connection with FIGS. 70, 70A, 71, 76, and 77. Accordingly, reference should be made to the description above in connection with FIGS. 70, 70A, 71, 76, and 77 for additional information regarding the structure and features, and possible alternatives to the structure and features of the collection tank illustrated in FIGS. 72-75 and described below. Structure and features of the embodiment shown in FIGS. 72-75 that correspond to structure and features of the embodiments of FIGS. 70, 70A, 71, 76, and 77 are designated hereinafter in the 4500 series of reference numbers.

Like the collection tank 4467 illustrated in FIGS. 70, 70A, 71, 76, and 77, the collection tank 4567 shown in FIGS. 72-75 has all interior chamber 4587 for fluid communication with flat tubes 4510, a number of receiving openings 4579 each having a rear portion 4585 for receiving the ends 4577 of flat tubes 4510, and a number of injections openings 4591 along the longitudinal sides (only one visible in FIGS. 72-75) of the collection tank 4567. FIG. 75 provides additional detail regarding the receiving openings 4579, including the rear portions 4585 used to receive and support the ends 4577 of the flat tubes 4510 (not shown in FIG. 75), and the injection openings 4591 in fluid communication with the receiving openings 4579.

The flat tubes 4510 received through the receiving openings 4579 define corresponding gaps 4593 between the interior surfaces of the receiving openings 4579 and the flat tube ends 4577. With particular reference to FIG. 73, the flow channels 4516 of each flat tube 4510 within a respective receiving opening 4579 are in fluid connection with the interior chamber 4587 of the collection tank 4567. FIG. 73 also illustrates the connections between the injection openings 4591 and the receiving openings 4579 for injecting adhesive 4589 (not shown) into the gap 4593 as described above.

As best shown in FIG. 74, the entrance of the receiving openings 4579 can be closed or substantially closed on one or more sides of each flat tube end 4477 by entrance walls 4599 (not shown in FIG. 75). The entrance walls 4599 can be defined by one or more elements of the collection tank 4567, such as by a plate in which are defined multiple openings that define the entrance of each receiving opening 4579 when the plate is installed with the multiple openings aligned with the receiving openings 4579. Alternatively, the entrance walls 4499 can be defined by terminal ends of the receiving opening walls that have been enlarged, flared, bent, or otherwise shaped to at least partially close the gaps 4593 described above. In some embodiments, the entrance walls 4599 are shaped to match or substantially match the cross-sectional shape of the flat tube ends 4577 received therein. Also, the entrance walls 4599 can be dimensioned to define a clearance fit with a flat tube end 4577, or can instead define an interference fit such that slight pressure can be exerted upon the collection tank 4567 and/or on the flat tubes 4510 to push the flat tubes 4510 past the entrance walls 4599 and into the rest of the receiving openings 4579. In this manner, seals at the entrances of the receiving openings 4579 can be provided between the collection tank 4567 and the flat tube ends 4577. These seals can be fluid tight or substantially fluid tight in some embodiments, and can prevent adhesive leakage during adhesive injection in some embodiments.

It should be noted that the construction of the collection tank 4567 illustrated in FIGS. 72-75 (and in the other figures) is only exemplary, and is not limiting to the scope of the present invention.

In some embodiments, the flat tube ends 4477, 4577 can be deformed. For example, the flat tube ends 4477, 4577 can be deformed such that the large diameter D of the flat tube 4410, 4510 is increased and the small diameter d of the flat tube 4410, 4510 is decreased at the flat tube ends 4477, 4577. Considering the relatively small wall thickness of the flat tubes 4410, 4510 in some embodiments, such deformation can be performed without a significant load on the walls of the flat tube 4410, 4510. In some embodiments, the dimensions of the periphery of the undeformed flat tube end 4477, 4577 remain substantially the same as those of the deformed flat tube end 4477, 4577. As a result, the walls of the flat tube 4410, 4510 in such embodiments do not undergo a significant expansion or contraction.

In some embodiments in which the flat tube ends 4477, 4577 are deformed, such deformation can be performed before the introduction of the flat tube ends 4477, 4577 into the corresponding receiving openings 4479, 4579 of the collection tank 4467, 4567. Examples of flat tube-to-collection tank connections in which the flat tube ends have been deformed will now be described in connection with FIGS. 78-83.

FIGS. 78-83 illustrate flat tube-to-collection tank connections according to three additional embodiments of the present invention. These embodiments employ much of the same structure and have many of the same properties as the flat tube-to-collection tank connection embodiments described above in connection with FIGS. 70-77. Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiments described above in connection with FIGS. 70-77. Reference should be made to the description above in connection with FIGS. 70-77 for additional information regarding the structure and features, and possible alternatives to the structure and features of the connection embodiments illustrated in FIGS. 78-83 and described below. Structure and features of the embodiments shown in FIGS. 78-83 that correspond to structure and features of the embodiments of FIGS. 70-77 are designated hereinafter in the 4600, 4700, and 4800 series of reference numbers, respectively.

In each of the embodiments illustrated in FIGS. 78-84, the flat tube ends 4677, 4777, 4877 are deformed, with the collection tanks 4667, 4767, 4867 having correspondingly shaped receiving openings 4679, 4779, 4879. Deformation of the flat tube ends 4677, 4777, 4877 shown in FIGS. 78-84 has been carried out alter the conclusion of the brazing process (Station II in FIG. 84)—before setting the flat tube ends 4677, 4777, 4877 into the receiving openings 4679, 4779, 4879.

In the embodiment of FIGS. 78-80, each flat tube 4610 has an end 4677 that is received snugly into a corresponding rear portion 4685 of a receiving opening 4679. In this embodiment, the broad sides 4622, 4624 of each flat tube 4610 have been expanded (i.e., bent away from one another) to define a flared flat tube end 4677, whereas the narrow sides 4618, 4620 have been compressed (i.e., bent toward one another). Also, each receiving opening 4679 also has a stops 4675 (see FIG. 80) for limiting insertion of the flat tubes 4610 to a desired distance.

Like the embodiment of FIGS. 78-80, in the embodiments of FIGS. 81-83, the broad sides 4722, 4724, 4822, 4824 of each flat tube 4710, 4810 have been expanded to define a flared flat tube end 4777, 4877, whereas the narrow sides 4718, 4720, 4818, 4820 have been compressed. However, that part of the collection tank 4767, 4867 defining the receiving openings 4779, 4879 has one or more slits 4773, 4873 extending alongside at least a portion of the receiving openings 4779, 4879, and in some embodiments extending around the receiving opening 4779, 4879. In either case, the slits 4773, 4873 are positioned and dimensioned to receive the free ends 4777, 4877 of the flat tubes 4710, 4810. The slits 4773, 4873 also function as stops to limit the depth of insertion of the flat tube ends 4777, 4877.

Following the insertion of the flat tube ends 4777, 4877 into the receiving openings 4779, 4879 and slits 4773, 4873, adhesive 4789, 4889 (not shown) can be injected into gaps 4793, 4893 between the flat tube ends 4777, 4877 and the interior surfaces of the receiving openings 4779, 4879. This injection can be performed in any of the manners described herein, and is performed by injection through injection openings 4791, 4891 in the illustrated embodiments of FIGS. 81-83 by way of example. In some embodiments, including those in which deformed flat tube ends are utilized, one or more inserts 4771 can be placed between the flat tube ends 4777 to help prevent deformation of the flat tube ends 4777 when the flat tube ends 4777 are exposed to internal pressure loads. For example, interior folds formed in the embodiment of FIGS. 1-5 can be protected from deformation when exposed to internal pressures by use of such inserts 4771. In the illustrated embodiment of FIGS. 81 and 83, for example, the inserts 4771 have a generally trapezoidal cross-sectional shape, although any other cross-sectional shape can be used depending at least in part upon the adjacent shapes of the flat tube ends 4777. The inserts 4771 can be introduced to their positions adjacent the flat tube ends 4777 before or after application of the adhesive 4789 (e.g., after Station III, or before or after Station IV in FIG. 84).

If used, the inserts 4771 can be manufactured of any material, including without limitation plastic or metal, can be solid or hollow, and in some embodiments can be defined by an easily deformable or flowable mass that is later hardened. Also, multiple inserts 4771 can be connected prior to and during insertion, such as to a common bar or rail to define a comb-like shape (not shown). This type of insertion, such as by a common bar or rail, can permit two or more, and in some embodiments all of the inserts 4771 to be placed in one step. In some embodiments, the connections between the common bar or rail and the inserts 4771 is frangible, enabling the common bar or rail to be removed subsequent to the insertion of the inserts 4771.

To enable insertion of the inserts 4771 in desired locations between adjacent flat tube ends 4777, either or both of the opposite longitudinal walls 4795 of the collection tank 4767 can have apertures (see FIG. 83, for example) aligned with these locations and dimensioned to enable insertion of the inserts 4771. In this regard, it should be noted that the inserts 4771 need not necessarily occupy an entire space between adjacent flat tube ends 4777, and need only occupy sufficient space between the flat tube ends 4777 to support the ends under pressure as needed.

It should be noted that the various manners of introducing adhesive to locations between the flat tube ends 4477, 4577, 4677, 4777, 4877 and the interior surfaces of the receiving openings 4479, 4579, 4679, 4779, 4879 described herein can be utilized regardless of whether the flat tube ends 4477, 4577, 4677, 4877 are deformed or undeformed.

In some embodiments of the present invention, the collection tank 4467, 4567, 4667, 4767, 4867 can includes stiffening walls 4469, 4569, 4669, 4769, 4869 extending between and/or at least partially defining walls of the receiving openings 4469, 4569, 4679, 4779, 4879 of the collection tank 4467, 4567, 4667, 4677, 4877. These stiffening walls 4469, 4569, 4669, 4769, 4869 can be used to strengthen parts of the collection tank 4467, 4567, 4667, 4767, 4867 as needed, and are not visible in all illustrated collection tank embodiments. For example, one or more stiffening walls 4669, 4769, 4869 can extend in the transverse direction of the collection tank 4667, 4767, 4867 (e.g., connecting the opposite longitudinal walls 4695, 4795, 4895 of the collection tank 4667, 4767, 4867), and can provide added strength and/or rigidity to the collection tank 4667, 4767, 4867. The stiffening walls 4669, 4769, 4869 can be formed in any manner, and can be integral to collection tank 4667, 4767, 4867 or separate elements connected thereto in any suitable manner. In some embodiments, the stiffening walls 4669, 4769, 4869 are formed during injection molding of the collection tank 4667, 4767, 4867, and are thus an integral part of the collection tank 4667, 4767, 4867.

Some embodiments of collection tanks 4667, 4767, 4867 according to the present invention can also or instead have stiffening walls extending longitudinally with respect to the collection tank 4667, 4767, 4867. For example, such stiffening walls can be formed between and connect walls defining receiving openings 4679, 4779, 4879 of the collection tank 4667, 4767, 4867. A cross-section of one such longitudinal stiffening wall 4469 is shown in FIG. 70A by way of example, and is located mid-way between the front and rear faces of the collection tank 4667, 4767, 4867 (although such longitudinal stiffening walls can be located in other positions as desired). Such longitudinally-extending stiffening walls 4469 can extend along any part or all of the length of the collection tank 4667, 4767, 4867 (interrupted as needed by the receiving openings 4679, 4779, 4879).

As mentioned above, the collection tank can be constructed of any number of parts connected together in any suitable manner. By way of example, FIGS. 72 and 82 illustrate collection tanks 4467, 4867 in which the collection tank 4467, 4867 is formed of two parts 4467 a, 4467 b, and 4867 a, 4867 b. In both illustrated embodiments, the parts 4467 a, 4467 b, and 4867 a, 4867 b are joined along a Z-shaped interface, and can be joined by welding or adhesive. Still other manners of establishing this connection are possible based at least in part upon the material used to form the collection tank 4467, 4867. In some embodiments, this connection is releasable, such as that shown in the embodiments of FIGS. 72-75 where clips on the collection tank 4467 can be used to releasably secure part of the collection tank 4467 a in place with respect to the remainder of the collection tank 4467 b.

The various flat tube embodiments described herein can be utilized in a number of different heat exchangers adapted for different uses. In so doing, the flat tubes can be modified from the embodiments illustrated in FIGS. 1-54 and/or can be assembled in heat exchangers in a variety of different manner to adapt the heat exchangers for particular applications.

FIGS. 85-90 illustrate four constructions of heat exchangers according to different embodiments of the present invention. Although still other heat exchanger embodiments are possible by modifying the number and arrangement of flat tubes and/or by modifying the types of flat tubes (e.g., tube size and shape, insert size and shape, and the like), each of the heat exchangers illustrated in FIGS. 85-91 provides unique advantages in many applications.

Before describing each of the heat exchangers 4963, 5053, 5163, 5263 illustrated in FIGS. 85-90 in greater detail, it should be noted that each of the flat tubes 4910, 5010, 5110, 5210 illustrated therein can be replaced with flat tubes 4910, 5010, 5110, 5210 having any of the shapes and constructed in any of the manners described above with reference to the embodiments of FIGS. 1-54, and that any of the heat exchanger assembly features and methods of assembly (e.g., regarding the flat tubes, core construction, and core-to-header attachment) also described herein in connection with the embodiments of FIGS. 1-84 can be utilized in the construction and manufacture of the heat exchangers 4963, 5063, 5163, 5263 illustrated in FIGS. 85-90. For example, each of the flat tubes 4910, 5010, 5110, 5210 illustrated in FIGS. 85-90 is a two-piece flat tube 4910, 5010, 5110, 5210 with insert 4934, 5034, 5134, 5234, wherein two separate pieces of sheet material are used to form each illustrated tube 4910, 5010, 5110, 5210, and wherein a third separate piece of sheet material is used to form the internal insert 4934, 5034, 5134, 5234. Although the particular two-piece flat tube constructions (with inserts) illustrated in FIGS. 85-90 are desirable for the applications described and still other applications, any of these flat tubes 4910, 5010, 5110, 5210 can be replaced by any of the one-piece or other two-piece flat tubes (with inserts) described above and/or illustrated herein in order to adapt the flat tubes 4910, 5010, 5110, 5210 and the resulting heat exchangers 4963, 5063, 5163, 5263 for any desired application. In this regard, a combination of flat tubes 4910, 5010, 5110, 5210 with inserts formed of different numbers of sheets can be used in the same heat exchanger 4963, 5063, 5163, 5263.

In the illustrated tube constructions of FIGS. 85-91 and any of the alternative tube constructions just mentioned, either or both narrow sides of the flat tube can be formed by adjacent overlapping longitudinal edges of material, depending at least in part upon the number of sheets of material used to construct the flat tube. Each pair of overlapping longitudinal edges therefore defines a reinforced narrow side of the flat tube. In some embodiments, either or both of the overlapping longitudinal edges of the flat tube can be folded one or more times to define even further material thickness at the narrow side(s) of the flat tube. In some of these embodiments, a reinforcing sheet of material defining the insert can have one or both longitudinal edges shaped to lie adjacent the overlapping longitudinal edges of the flat tube, thereby providing an additional layer of material for tube reinforcement at the narrow sides. Also, either or both longitudinal edges of the insert can be folded to have a multiple-layered thickness lying adjacent the overlapping longitudinal edges of the flat tube, thereby providing still further reinforcement at either or both narrow sides. Accordingly, either or both narrow sides of the flat tubes can exhibit a thickness which amounts to at least twice, and in some embodiments more than twice the thickness of the sheet material used to form the flat tube walls, which can be formed by rolling thicker sheet material, in some embodiments.

As described in greater detail above, in those embodiments in which flat tubes are constructed of a single part (with or without an insert), reinforcement of the narrow sides can be achieved by rounding one or more folds of the sheet of material to form the first narrow side of the flat tube, and overlapping the opposite longitudinal edges of the sheet of material to form the second narrow side of the flat tube (e.g., by receiving or encompassing a bend of one longitudinal edge into a larger bend of the other longitudinal edge, or in other manners described herein).

In some one-piece flat tube embodiments, one sheet of material can form the exterior walls of the flat tube as well as the interior flow channels. In such embodiments, a gradation can be located at bends of the sheet of material (defining the narrow sides of the flat tube) at which a longitudinal edge of the sheet of material comes to rest so that the exterior surface of the flat tube remains as smooth as possible. Additionally, in those embodiments in which the insert is defined by a separate sheet of material, the two longitudinal edges of this separate sheet of material can be rounded or otherwise shaped to be received within the narrow sides of the flat tube (e.g., see the illustrated embodiment of FIG. 46).

As also described in greater detail above, in those embodiments in which flat tubes are constructed of two separate parts (with or without an insert), the two separate parts can be constructed identically, in which cases one longitudinal edge of each part can have a bend encompassing a smaller bend of an adjacent longitudinal edge of the other part. These two separate parts can therefore be transposed with respect to one another in order to form the flat tube. In other embodiments, the two separate parts are not identical to one another, and have opposite longitudinal edges joined together in any of the manners described herein (including without limitation nested arc-shaped longitudinal edges).

Also, the substantially planar broad sides of any of the tube embodiments described and/or illustrated herein can be used to provide improved brazed joints for fins attached thereto, thereby resulting in improved heat exchange efficiency of the heat exchanger 4963, 5053, 5163, 5263.

Also in any of the two-piece and three-piece flat tube constructions that can be employed in the heat exchangers of FIGS. 85-89, the internal insert can be corrugated or otherwise shaped to define two or more flow channels through the flat tube. The internal insert can have corrugations with different shapes and/or sizes at different locations across the width of the insert in order to define two or more laterally disposed regions of flow channels having different shapes and/or sizes (e.g., see FIGS. 85-89, for example). More broadly, the internal insert can be shaped to define regions of flow channels having different shapes and/or sizes in different locations across the width of the two-piece or three-piece flat tube. In some embodiments, the different regions of flow channels can be isolated from one another, whereas in other embodiments the different regions are in fluid communication with one another (e.g., at one or more locations along the length of one or more flow channels). Also, in some embodiments, each of the flow channels in a region is isolated from the other flow channels in the same region along the length of the flat tube, whereas in other embodiments, the flow channels within the same region are in fluid communication with one another (e.g., via openings between adjacent flow channels), but are isolated from other flow channels in other regions.

It will be appreciated that many of the advantages of using the flat tubes 4910, 5010, 5110, 5210 according to the present invention in the illustrated embodiments of FIGS. 85-89 relate to the ability to manufacture such flat tubes at lower cost, with reduced amounts of material, and/or with improved heat exchange performance. These advantages are realized by the use of sheet materials having the relatively low thicknesses described above for forming the flat tubes and inserts. Although any of the material thicknesses of the flat tubes described above can be used in the embodiments of FIGS. 85-89, the sheet material used to form the walls of the flat tubes in the illustrated embodiments has a thickness of no greater than about 0.15 mm (0.0059055 in). Also, this sheet material has a thickness of no less than about 0.03 mm (0.0011811 in.). These types of wall thicknesses can be used to withstand compressive loads and can exhibit relatively good internal pressure stability in many embodiments in light of the fact that the insert can be brazed to the broad walls of the flat tube. Similarly, although any of the material thicknesses of the inserts described above can be used in the embodiments of FIGS. 85-89, the sheet material used to form the inserts in the illustrated embodiments has a thickness of no greater than about 0.09 mm (0.003543 in). Also, this sheet material has a thickness of no less than about 0.03 mm (0.0011811 in.).

By utilizing the various flat tube constructions for the illustrated heat exchangers 4963, 5053, 5163, 5263 and for other heat exchanger designs, advantages of increased production speed and/or reduced material and assembly costs can be realized. For example, based upon the relatively low amount of sheet deformation needed to form the various one- or two-piece flat tubes according to the present invention described above, the flat tubes can be produced more economically on a tube mill (e.g., manufacturing lines 3701 and 1900, for example) even at high operating speeds using endless sheets of material. Moreover, with relatively low modification expenditure, heat exchangers having nearly any depth can be manufacturing using the same source of flat tubing (e.g., continuous or endless tubing and finned tubing produced as described above, for example).

The heat exchangers 4963, 5063, 5163, 5264 illustrated in FIGS. 85-90 are presented not only to illustrate heat exchanger embodiments that provide good performance results in many applications, but also to illustrate a number of heat exchanger features that can be utilized alone or in combination in heat exchangers according to other embodiments of the present invention. Such features include, without limitation, collection tanks that are internally divided to direct separate flows through different internal regions of the same flat tubes, and possible flow arrangements through the heat exchanger.

With reference now to the heat exchanger 4963 illustrated in FIG. 85, the heat exchanger 4963 has a single row of flat tubes 4910 having a depth T (generally similar to the large diameter D of each flat tube 4910). Although any of the other large and small diameters D, d described above can be used for the flat tubes 4910, the large diameter D of the flat tubes 4910 shown in FIG. 85 is no greater than about 300 mm (11.811 in). In some embodiments, a large diameter D of no less than about 10 mm (0.3937 in) is used to provide good performance results. Also, the small diameter d of the flat tubes 4910 shown in FIG. 85 is no greater than about 15 mm (0.59055 in). In some embodiments, a small diameter d of no less than about 0.7 mm (0.02756 in) is used to provide good performance results. These dimensions of the flat tubes 4910 in the illustrated embodiment of FIG. 85 are particularly suitable for heat exchangers 4963 in motor vehicles. However, other applications are possible and fall within the spirit and scope of the present invention.

The heat exchanger 4963 illustrated in FIG. 85 is adapted to cool two or three fluids by means of a common flow of cooling fluid (e.g., air) passing between the flat tubes 4910. The cooling air is illustrated in FIG. 86 as a double block arrow which flows through fins (not shown) between the flat tubes 4910.

According to the illustrated embodiment of FIG. 86, cooling air can flow either from left to right or vice versa through the cooling network defined by the tube-fin block 4965. Each of the flat tubes 4910 includes four interior regions 4975 a, 4975 b, 4975 c, 4975 d at different locations along the width of the flat tube 4910. The four illustrated interior regions 4975 a, 4975 b, 4975 c, 4975 d have the same or substantially the same width, although interior regions 4975 a, 4975 b, 4975 c, 4975 d of different widths are possible in other embodiments. Also, each illustrated interior region 4975 a, 4975 b, 4975 c, 4975 d has a number of flow channels 4916 a, 4916 b, 4916 c, 4916 d, each having a different shape and/or size from the flow channels 4916 a, 4916 b, 4916 c, 4916 d of the other interior regions 4975 a, 4975 b, 4975 c, 4975 d. The shape and size of the flow channels 4916 a, 4916 b, 4916 c, 4916 d in each interior region 4975 a, 4975 b, 4975 c, 4975 d is at least partially defined by the shape of the insert 4934 in that interior region 4975 a, 4975 b, 4975 c, 4975 d. Although the insert varies in shape from interior region to interior region 4975 a, 4975 b, 4975 c, 4975 d in the illustrated embodiment, each flat tube 4410 is substantially the same as the others in the heat exchanger 4963.

Although four interior regions 4975 a, 4975 b, 4975 c, 4975 d are employed in the heat exchanger 4963 illustrated in FIG. 85, any number of interior regions 4975 a, 4975 b, 4975 c, 4975 d can be defined by one or more of the flat tubes 4910 in other embodiments, and can have any relative sizes desired. Also, although each portion of the insert 4934 in each interior region 4975 a, 4975 b, 4975 c, 4975 d of the flat tube 4910 illustrated in FIG. 85 has a shape different from that in the other interior regions 4975 a, 4975 b, 4975 c, 4975 d (thereby defining flow channels 4916 a, 4916 b, 4916 c, 4916 d that are different in each interior region 4975 a, 4975 b, 4975 c, 4975 d), in other embodiments two or more of the interior regions 4975 a, 4975 b, 4975 c, 4975 d can have identical or substantially identical flow channels 4916 a, 4916 b, 4916 c, 4916 d.

With continued reference to FIG. 85, in some embodiments, each flat tube 4410 in a heat exchanger 4963 or section of the heat exchanger 4963 has the same number of interior regions 4975 a, 4975 b, 4975 c, 4975 d with flow channels 4916 a, 4916 b, 4916 c, 4916 d having the same or substantially the same shape and size. However, this in not necessarily the case in other embodiments. The number, size and shapes of regions within each flat tube 4910 and in a set of flat tubes 4910 can be determined based at least in part upon the requirements of the application.

The heat exchanger 4963 of FIG. 85 includes two collection tanks 4967 a and 4967 b. One collection tank 4967 a includes three dividing walls 4973 a, 4973 b, and 4973 c, which extend in a direction substantially perpendicular to the depth T of the heat exchanger 4963, and which run lengthwise with respect to the collection tanks 4967 a, 4967 b. The other collection tank 4967 b includes two dividing walls 4973 d and 4973 e.

FIG. 85 illustrates a number of arrows indicating the directions of flow through the heat exchanger 4963. On the left side (with respect to FIG. 85), a medium flows into the first collection tank 4967 a and through the first interior region 4975 a of each flat tube 4910. A second medium flows in the first collection tank 4967 a and through the second interior region 4975 b of each flat tube 4910, and is separated from the flow of the first medium through the first interior regions 4975 a by a first dividing wall 4973 a therein. The second medium is also separated from the first medium at the second collection tank 4967 b by the first dividing wall 4973 d therein, and from a third medium (which can be a second pass of the first medium through the heat exchanger 4963, in some embodiments, or another medium in other embodiments) at the second collection tank 4967 b by the second dividing wall 4973 e therein. The middle dividing wall 4973 b of the first collection tank 4967 a separates the flow of the second medium entering the heat exchanger 4963 from the return flow of the second medium exiting the heat exchanger 4963 after passing through the third interior region 4975 c of each flat tube 4910. The third medium passes through the heat exchanger 4963 by flowing through the fourth interior region 4975 d of each flat tube 4910, and is separated from the second medium in the first collection tank 4967 a by the third dividing wall 4973 c therein.

In some applications of the heat exchanger 4963 just described, the left section of the heat exchanger 4963 (with reference to the perspective of FIG. 85) can be a high temperature region for charge air. Charge air exiting this section of the heat exchanger 4963 after passing through the first interior region 4975 a of each flat tube 4910 can flow back into the heat exchanger 4963 in some embodiments, passing through the fourth interior region 4975 b of each flat tube 4910 in the right section of the heat exchanger 4963. Accordingly, this return flow can then be a low temperature region for charge air. In such embodiments, cooling fluid passing between the flat tubes 4910 can flow from right to left in the illustrated embodiment of FIG. 85. In the middle section of the heat exchanger 4963, a high temperature cooling fluid can enter into the first collection tank 4967 a, pass through the second interior region 4975 b of each flat tube 4910, and return via the second collection tank 4967 b and through the third interior region 4975 c of each flat tube 4910 to exit the heat exchanger 4963. The return pass of this fluid (upstream of the first pass, as referenced with respect to the direction of flow of cooling fluid passing between the flat tubes 4910) therefore defines a low temperature coolant region. In some embodiments, 10% of this fluid passing through the second and third interior regions 4975 b, 4975 c can flow through these regions again in order to further reduce its temperature, although other percentages (including none) are possible in other embodiments. Also, in other embodiments, any number of dividing walls 4973 a, 4973 b, 4973 c, 4973 d, 4973 e in any number of collection tanks 4967 a, 4967 b having any number of fluid inlet and outlet ports can be arranged in other manners to provide other heat exchanger designs and functions.

FIG. 86 illustrates a heat exchanger 5063 according to another embodiment of the present invention, in which flat tubes 5010 having the features shown in FIG. 87 are used. The illustrated heat exchanger 5063 is adapted for use in a vehicular cooling fluid radiator, although other applications for the heat exchanger 5063 are possible. This heat exchanger 5063 includes an interior region 5075 a, which can be a high temperature region in some embodiments, based upon the fact that the temperature of the cooling fluid therein is relatively high. The heat exchanger 5063 can also include a low temperature interior region 5075 b, in which the temperature of at least part of the cooling fluid leaving the first interior region 5075 a can be further decreased.

More detail regarding the flat tubes 5010 illustrated in FIG. 86 can be seen in FIG. 87, which shows a flat tube 5010 according to an embodiment of the present invention that can be used in the heat exchanger 5063 of FIG. 86. Although the flat tube 5010 illustrated in FIG. 87 provides unique performance results, it should be noted that any of the other flat tube embodiments disclosed herein can instead be used. The flat tube 5010 illustrated in FIG. 87 is formed of two separate sheets of material, each of which form first and second portions 5012, 5014 of the two-piece tube 5010. A third sheet of material is used to form the insert 5034. The first and second portions 5012, 5014 in the illustrated embodiment are identical or substantially identical, but are transposed with respect to one another. In the manufacturing process, a larger bend defining a larger arc portion is formed on one longitudinal edge of each portion 5012, 5014, and encompasses a smaller arc portion formed on a corresponding longitudinal edge of the other portion 5014, 5012, so that the two narrow sides 5018, 5020 of the flat tube 5010 each have a double wall thickness. Furthermore, the opposite longitudinal edges 5038, 5040 of the insert 5034 are shaped to fit within the inside narrow sides 5018, 5020 of the flat tube 5010. In this particular construction, a three-layer thickness is defined on one narrow side 5018. This thickness can be three times that of the material used to form the first and second portions 5012, 5014 in those embodiments in which the material thickness of the insert 5034 is the same as that used for the first and second portions 5012, 5014, although the insert 5034 can be made of thinner material in other embodiments. It should be noted that the features shown in FIG. 87 can be applied in any of the other flat tube embodiments described and/or illustrated herein.

The two interior regions 5075 a, 5075 b of the flat tubes 5010 in the heat exchanger of FIG. 86 are defined at least in part by the corresponding section of the insert 5034 within each interior region 5075 a, 5075 b. The first interior region 5075 a can be utilized in some embodiments to support relatively higher pressures than fluid in the second interior region 5075 b, by virtue of the relatively narrow flow channels 5016 defined by the narrower spaces between corrugations of the insert 5034 in the first interior region 5075 a. Also, the second narrow side 5020 corresponding to the second interior region 5075 b has greater reinforcement than the opposite (first) narrow side 5018. This reinforcement is formed by a longitudinal edge 5040 of the insert 5034 having two additional folds at the second narrow side 5020, thereby providing the second narrow side 5020 with five layers of material. This design provides an example of how flat tubes 5010 according to the present invention can be reinforced where necessary due to anticipated stresses in selected areas of the flat tubes 5010, and can be provided with thinner wall areas (e.g., 0.03 mm-0.15 mm (0.0011811-0.0059055) in some embodiments) in other areas where anticipated stresses are relatively low. The weight of materials used to construct the flat tubes 5010 and manufacturing losses of the heat exchanger 5010 can therefore be considerably reduced.

FIG. 88 illustrates a heat exchanger according to another embodiment of the present invention, utilizing the flat tubes 5110 illustrated in FIG. 89. In the illustrated embodiment of FIGS. 88 and 89, the inside region 5175 of each flat tube 5110 has a number of flow channels 5116 defined at least in part by an insert 5134 that is uniformly shaped or substantially uniformly shaped across the width of the insert 5134. However, the heat exchanger 5163 is provided with two different groups G1, G2 of flat tubes 5110 having flow channels 5116 that are different from one another. In other embodiments, any number of such groups are possible. Fluid flowing into or out of each group G1, G2 of flat tubes 5110 is separated from that of the other group G2, G1 by a transverse dividing wall 5173 in the collection tank 5167 extending in the direction of the depth of the heat exchanger 5163. Different fluids can flow in each group G1, G2 of flat tubes 5110. For example, in one group G1, a first media (e.g. oil) can flow, while in the other group G2, a second media (e.g. cooling fluid) can flow. The flat tubes 5110 of group G2 are generally adapted for a medium which is under higher pressure than that in the flat tubes 5110 of group G1, as can be seen from the use of narrower flow channels 5116 and smaller distances between walls of the insert 5134 in the flat tubes 5110 of group G2, and the larger degree of reinforcement of the narrow sides 5118, 5120 in the flat tubes 5110 of group G2 for relatively more stability. In some applications, the flat tubes 5110 of the group G2 can define a low temperature cooling fluid radiator portion of the heat exchanger 5163, while the flat tubes 5110 of the group G1 can define a high temperature cooling fluid radiator portion of the heat exchanger 5163.

Under the assumption that the medium in the flat tubes 5110 of group G2 is under a higher pressure than the medium in the flat tubes 5110 of group G1, the broad sides 5122, 5124 and the narrow sides 5118, 5120 of the flat tubes 5110 of group G2 are reinforced by the design of the insert 5134 used therein. In particular, the corrugations of the inserts 5134 in the flat tubes 5110 of group G2 are significantly narrower than those of the flat tubes 5110 in group G1. Additionally, the narrow sides 5118, 5120 of the flat tubes 5110 in group G2 have five layers of material (two defined by overlapping longitudinal edges of the first and second tube portions 5112, 5114 at the narrow sides 5118, 5120, and three defined by two folds on each longitudinal edge 5138, 5140 of the insert 5134), whereas only three layers of material are located at the narrow sides 5118, 5120 of the flat tubes 5110 in group G1 based upon the lack of such insert folds. It should be noted that the flat tubes 5110 within both groups G1, G2 can be identical or substantially identical, and can both be equally adapted to receive the different types of inserts 5134 shown in FIG. 89. Accordingly, the two different interior regions 5175 in the flat tubes 5110 are created in this particular embodiment by different inserts 5134 defining two different groups of flat tubes 5110 for the heat exchanger 5163.

FIG. 90 illustrates a heat exchanger according to yet another embodiment of the present invention, utilizing flat tubes 5210 similar to that of FIG. 53. In this particular embodiment, the relative sizes of the interior regions 5275 a, 5275 b varies between the flat tubes 5210 of the heat exchanger 5263. In some embodiments (including the illustrated embodiment of FIG. 90, for example), the relative sizes of the interior regions 5275 a, 5275 b varies gradually from flat tube 5210 to flat tube 5210 across at least a portion of the heat exchanger 5263. Accordingly, a collection tank 5267 secured to the flat tubes 5210 can have a dividing wall 5273 a extending obliquely with respect to the ends of the flat tubes 5210. The position of this dividing wall 5273 a can correspond to the changing size of the interior regions 5275 a, 5275 b in the flat tubes 5210. If desired, one or more additional dividing walls (e.g., dividing wall 5273 b shown in FIG. 90) can be included in the collection tank 5267 to provide further separations of flow through the heat exchanger 5263 as desired.

An example of a one-piece flat tube 5310 that can be utilized in any of the heat exchanger embodiments described above is shown in FIG. 91 by way of example. The one-piece flat tube 5310 in FIG. 91 is substantially the same as that shown in FIG. 54 described earlier, with the exception of insert corrugations 5252 that are substantially rectangular in the embodiment of FIG. 91 (as opposed to the substantially triangular corrugations 4352 in the embodiment of FIG. 54), and with the exception of flow channels 4316, 5316 having the same size in FIG. 54, and having different sizes in FIG. 91. Accordingly, reference is hereby made to the description accompanying FIG. 54 for more information regarding the flat tube embodiment illustrated in FIG. 91.

The flat tubes 4310, 5310 in FIGS. 54 and 91 can be produced from a single sheet of material, and can be used in place of any of the flat tubes in the embodiments described above in connection with FIGS. 85-90. It should also be noted that any of the other one-piece and two-piece flat tubes disclosed herein can be used in place of any of the flat tubes in the embodiments described above in connection with FIGS. 85-90. The narrow sides 4318, 4320, 5318, 53210 of both flat tubes 4310, 5310 illustrated in FIGS. 54 and 91 include a double thickness of the sheet of material used to form the flat tube 4310, 5310. The sheet of material can be folded twice in the two areas of the sheet of material that will be bent to form the narrow sides 4318, 4320, 5318, 5320 of the flat tube 4310, 5310 (i.e., the areas adjacent and flanking that portion of the sheet of material shaped to define the integral insert 4334, 5334), thereby increasing the thickness of the narrow areas by three times that of the original material thickness. Furthermore, each longitudinal edge of the sheet of material can be bent and moved to encompass a respective reinforced section in the manner shown in FIGS. 54 and 91. Both of these reinforced sections can be provided with a gradation 4358, 4360 (not visible in FIG. 91, but visible in FIG. 54) for receiving the corresponding longitudinal edges in a recessed manner. In order to further reinforce the narrow sides 4318, 4320, 5318, 5320 of the flat tube 4310, 5310, additional folds can be incorporated into the reinforced sections shown in FIGS. 54 and 91. In the flat tube 5310 illustrated in FIG. 91, two groups of flow channels 5316 are defined, each having a size that is different from those of the other group. In contrast, all the flow channels 4316 in the illustrated embodiment of FIG. 54 are substantially the same in size.

FIGS. 19-23 show a number of different flat tubes that can be produced from a single sheet of material. Like the other one-piece flat tubes illustrated herein, each of the embodiments shown in FIGS. 19-23 are especially suitable for the heat exchangers 4963, 5063, 5163, 5263 discussed in connection with FIGS. 85-90. In particular, the flat tubes described above in connection with FIGS. 19-23 include narrow sides that are reinforced by the provision of vertical or horizontal folds. Additionally, FIG. 46 illustrates a flat tube 3710 that can be produced from a single piece of sheet material, with an insert 3734 that can be produced from another separate sheet of material. This particular flat tube 3710 can also serve as a replacement for any of the flat tubes 4910, 5010, 5110, 5210 described above with respect to FIGS. 85-90. As described in greater detail above, in the embodiment of FIG. 46, one reinforced narrow side 3718 is formed by bending a portion of the sheet of material having additional folds. The other reinforced narrow side 3720 is formed by one longitudinal edge of the sheet of material encompassing the opposite longitudinal edge of the same sheet of material. This other narrow side 3720 can also be distinguished by the fact that either or both longitudinal edges of the sheet of material can be folded for further reinforcement. The second sheet of material can be provided with a number of corrugations as described above, and can also be provided with bends or folds at either or both longitudinal edges 3738, 3740 for further interior reinforcement of either or both narrow sides 3718, 3720.

FIGS. 92-95 illustrate exemplary heat exchanger structures and methods for connecting sheets of material to form a heat exchanger or a portion of a heat exchanger (e.g., a heat exchanger core, a portion of a heat exchanger core, a tube insert, heat exchanger tubes, the ribs or fins of a heat exchanger, the header of a heat exchanger, and the like). For example, in the illustrated embodiments of FIGS. 93-95, fins 8313 are brazed to a heat exchanger tube 8310. In these illustrated embodiments, the heat exchanger lubes 8310 are formed from a generally planar first sheet of material 8317, and the fins 8313 are formed from a second sheet of material 8333 having a corrugated shape. In other embodiments, the sheets of material being brazed are different portions of the same sheet of material. Also, in other embodiments and as explained in greater detail below, the heat exchanger tubes 8310 and/or the fins 8313 can have different shapes.

Although the methods described herein are with reference to the production of particular heat exchanger embodiments described in this patent application, such is by way of example only. Accordingly, it is to be understood that the processes described with reference to FIGS. 92-95 can be applied for the manufacture of all heat exchangers and portions of heat exchangers described in this application.

As explained above, the relatively small sheet material thickness of the heat exchanger tubes 8310 and/or the fins 8313 in some embodiments of the present invention can provide significant advantages relating to the overall performance of the heat exchanger, manufacturability, and possible wall constructions (as disclosed herein) that are not possible using thicker wall materials. Also, by utilizing one or more of the flat tube features described herein, the inventors have discovered that a number of different flat tubes having various characteristics adapted for a variety of applications can be constructed using significantly reduced material while retaining strength and heat exchange properties of heavier conventional flat tubes. Moreover, while reference is made herein to flat heat exchanger tubes, the present invention can also or alternatively be applied to heat exchanger tubes having different cross-sectional shapes including without limitation round, rectangular, triangular, or other polygonal shapes, irregular shapes, and the like.

In some embodiments, the heat exchanger tubes 8310, the heat exchanger fins 8313, and/or other portions of a heat exchanger can be formed from sheets of material having the same or substantially the same thickness. Alternatively, in other embodiments, two or more portions of the heat exchanger can be formed from sheets of material having different thicknesses. In some of these other embodiments, the heat exchanger tubes 8310 can be formed from sheets of material 8317 having a first thickness, and the heat exchanger fins 8313 can be arranged between adjacent tubes 8310 and can be formed from sheets of material 8333 having a different thickness. In such embodiments, a first portion of the heat exchanger (e.g., a header) can be formed from sheets of material having a first thickness, a second portion of the heat exchanger (e.g., at least one of the tubes) can be formed from sheets of material having a second thickness, and a third portion of the heat exchanger (e.g., the fins 8333) can be formed from sheets of material having a third thickness.

For example, in some embodiments of the present invention, a flat tube 8310 can be formed from sheets of material 8317 having a thickness of no greater than about 0.20 mm (0.007874 in). However, in other embodiments and as mentioned above, the inventors have discovered that heat exchanger tubes formed from sheets of material having a thickness of no greater than about 0.15 mm (0.0059055 in) provides significant advantages relating to the overall performance of flat tubes and heat exchangers made from such material, manufacturability, and possible wall constructions (as disclosed herein) that are not possible using thicker wall materials. Alternatively or in addition, the fins 8313 can be formed from sheets of material 8333 having a thickness of no greater than about 0.20 mm (0.007874 in). In other embodiments, the fins 8313 can be formed from sheets of material 8333 having a thickness of no greater than about 0.15 mm (0.0059055 in). In still other embodiments, the fins 8313 can be formed from sheets of material 8333 having a thickness in the range of approximately 0.03-0.15 mm (0.0011811-0.0059055 in) or slightly higher. In yet other embodiments, heat exchanger fins 8313 can be formed from sheets of material 8333 having a thickness of no greater than about 0.03-0.09 mm (0.0011811-0.0035433 in).

As shown in FIGS. 92-95, a first sheet of material 8317 manufactured according to some embodiments of the present invention can include a braze layer 8335 providing at least a portion of an outer surface X1 of the first sheet of material 8317, an inner sacrificial layer or corrosion protection layer 8337 disposed under the braze layer 8335 or a portion of the braze layer 8335, and a core 8315 disposed under the sacrificial layer 8337 (shown as a single layer in FIGS. 92 and 94, and as having two or more layers in FIGS. 93 and 95). As used herein and in the appended claims, terms such as “under”, “beneath”, “over”, and “above” are used only for ease of description, and do not alone indicate or imply that the structure referred to must have any particular orientation taken alone or employed in any structure.

The core 8315 in the illustrated embodiments of FIGS. 92-95 comprise an aluminum alloy by way of example. The aluminum alloy can have suitable amounts of one or more other materials, such as manganese, magnesium, titanium, copper, and the like, used to increase the strength and/or corrosion resistance of the core 8315, or for changing one or more other characteristics of the core 8315 as desired.

In some embodiments, the core 8315 is changed to produce a layer 8339 (sometimes referred to herein as a sub-layer of the core 8315) having one or more different properties than the rest of the core 8315. For example, by diffusing silicon within an upper portion of the core 8315 at an elevated temperature, such as during a brazing process, the structure and/or composition of the aluminum alloy in the upper portion can change to define the layer 8339 in which the silicon diffused (see FIG. 93, which illustrates such a process performed on the structure of FIG. 92). In some embodiments, this change can occur by the production of intermetallic compounds comprising the silicon, such as a silicon-manganese aluminum intermetallic compound. In so doing, one or more components of the aluminum alloy in the layer 8339 (e.g., manganese, by way of example only) can accumulate while the sheet of material 8317 is heated sufficiently to permit such accumulation, resulting in a modified layer 8339 of the core 8315 in which intermetallic compound has accumulated in locations throughout the modified layer 8339. In some embodiments, the silicon can facilitate this accumulation, such as by drawing one or more of the alloy components out of solid solution, or facilitating this accumulation in other manner.

The thickness of the modified layer 8339 can be dependent upon the temperature at which the above-referenced diffusion occurs and the time permitted for such diffusion to occur (e.g., the duration of a brazing cycle). In some embodiments, the modified layer 8339 is anodic with respect to the rest of the core 8315. For example, in those embodiments in which manganese has been drawn out of solid solution and has accumulated as an intermetallic as a result of silicon diffusion into the core 8315, the resulting modified layer 8339 can be anodic with respect to the rest of the core 8315.

With continued reference to the embodiments of FIGS. 91-95, and as described above, the illustrated sheet of material 8317 includes one or more sacrificial layers 8337 (one in FIGS. 92 and 93, and two in FIGS. 94 and 95). Each sacrificial layer 8337 can include a metal material, and can be a relatively pure or unalloyed metal material. In some embodiments, the sacrificial layer 8337 comprises an aluminum alloy through which silicon diffuses at a slower rate than that though the underlying core material 8315, and has a corrosion potential as described herein. For example, in some embodiments, the sacrificial layer 8337 comprises an aluminum alloy through which silicon diffuses at no more than 50% of the rate at which silicon diffuses though the underlying core material 8315. In other embodiments, the sacrificial layer 8337 comprises an aluminum alloy through which silicon diffuses at no more than 70% of the rate at which silicon diffuses though the underlying core material 8315. In this regard, the sacrificial layer 8337 can have trace amounts of one or more additional materials (e.g., iron, copper, zinc, manganese, magnesium, like metals, and combinations of such metals, by way of example). In some embodiments, the sacrificial layer 8337 has a corrosion potential that is substantially similar to the corrosion potential of the adjacent residual braze material of the braze layer 8335 following a brazing process. In this regard, it should be noted that following a brazing process, a residual amount of braze material can remain on any portion or all of the sheet of material 8317. Also in some embodiments, the material of the sacrificial layer 8337 is anodic to the material of the core 8315 (e.g., to the modified layer 8339 and/or to the rest of the core 8315).

In some embodiments, the braze layer 8335 comprises a aluminum-silicon alloy brazing material. In other embodiments, other brazing materials can also or alternatively be used, some of which comprise silicon. The braze layer 8335 can extend across substantially the entire outer surface of the sheet of material 8317, or can instead extend across less than the entire outer surface (e.g., across intended brazing locations only) of the sheet of material 8317. The braze layer 8335 can be part of the sheet of material 8317 to be used in a brazing operation, or can be deposited upon and/or formed by a portion of the sheet of material 8317 during the brazing process. In either case, the residual brazing material of the braze layer 8335 following a brazing process can be anodic to the material of the sacrificial layer 8337.

Any of the layers and/or sub layers of the sheet of material 8317 described herein and/or illustrated in FIGS. 92-95 can be secured together by roll bonding. By way of example only, the sub-layer 8339 of the core 8315 described above can be produced by roll bonding a layer of material having the sub-layer properties described above onto another layer of material to produce the core 8317 illustrated in FIG. 93.

As will now be explained, sheets of material 8317 formed according to the present invention can reduce and/or prevent corrosion (such as pitting corrosion, by way of example). In some embodiments, one or more of the layers and sub layers of the sheet of material 8317 (e.g., the braze layer 8335, the sacrificial layer 8337, the sub layer 8339, and/or the rest of the core 8315) can be formed from a material or alloyed with a material such that it is anodic to one or more of the underlying layers or sub layers of the sheet of material 8317. For example, in some embodiments, each of the layers and sub layers of the sheet of material 8317 (i.e., residual braze material of the braze layer 8335 following a brazing process, the sacrificial layer 8337, the sub layer 8339, and/or the rest of the core 8315) can be formed from a material or alloyed with a material such that it is anodic to an underlying layer or sub layer and is cathodic to an adjacent overlying layer or sub layer after brazing.

In some embodiments, one or more layers and sub layers of the sheet of material 8317 (i.e., the braze layer 8335, the sacrificial layer 8337, the sub layer 8339, and/or the rest of the core 8315) is formed from a material or alloyed with a material such that there is a difference of at least about 30 millivolts between one or more of the underlying layers or sub layers. For example, in some embodiments, each of the layers and sub layers of the sheet of material 8317 (e.g., the braze layer 8335, the sacrificial layer 8337, the sub layer 8339, and/or the rest of the core 8315) can be formed from a material or alloyed with a material such that there is a difference of at least about 30 millivolts between each adjacent layer, or between layers or sub-layers separated from one another.

As mentioned above, in some embodiments the core 8315 include titanium. In sufficient quantities, titanium can form dendrites during casting of the core 8315, resulting in layers of titanium-rich aluminum disbursed throughout the core 8315. Depending at least in part upon the manner in which the sheet of material defining the core 8315 is produced, the titanium-rich aluminum can be located primarily in the sacrificial layer 8337, primarily in the rest of the core 8315, or fully throughout the core 8315. In some embodiments, the titanium-rich aluminum can form sub-layers in the core 8315, and can serve as another measure of resistance to core material corrosion. Such sub-layers can also be cathodic to adjacent portions of the core 8315 for further corrosion resistance.

In those embodiments in which titanium-rich aluminum is formed in sub-layers of the core material as just described, the titanium-rich aluminum can help increase corrosion resistance by forcing corrosion to propagate in directions parallel or substantially parallel to the core 8315, or in directions parallel or substantially parallel to the titanium-rich aluminum sub-layers, thereby helping to slow or reduce pitting corrosion. In some embodiments, the material of the core 8315 comprises about 0.05-0.30 wt-% titanium. In other embodiments, a core layer 8315 having about 0.10-0.25 wt-% of titanium provides good strength and corrosion resistance performance. However, in many embodiments, a sheet of material 8317 having a core 8315 with a core layer 8315 having a titanium content of approximately 0.20 wt-% or slightly higher provides improved overall performance.

In some embodiments, the sheet of material 8317 has a thickness of no greater than about 0.15 mm (it being noted that any of the relatively thin tube wall and insert material thicknesses disclosed herein can be used). For example, the sheet of material in the illustrated embodiment of FIGS. 92 and 93 has a thickness of approximately 100 μm (3.937 mil). As described above, some embodiments of the present invention have a modified core sub-layer 8339 that can be produced by diffusion of silicon therein. The silicon can diffuse from the sacrificial layer 8337 or from the brazing material 8335 into the core 8315 in such embodiments. Such diffusion can take place during a brazing process. In light of the fact that the rate of diffusion into the core 8315 can at least partially determine the resulting depth of the modified core sub-layer 8339, control of such diffusion is possible by the sacrificial layer 8337. In this regard, the sacrificial layer 8337 can function to impede (but not stop) such silicon diffusion, and can comprise a material (e.g., an aluminum alloy more resistant to silicon diffusion and having the corrosion potential as described above) in which silicon diffuses at a slower rate than the material of the core 8315. By utilizing such a sacrificial layer 8337, silicon diffusion can be limited to a depth of 50 μm (1.969 mil) while still permitting sufficient brazing time at a sufficiently high brazing temperature to braze the fin 8313 to the sheet of material 8317. In some embodiments, the manufacturing process described herein can prevent or significantly reduce diffusion beyond a depth of 30 μm (1.181 mil).

In embodiments in which two or more portions of the heat exchanger are secured together, a second portion of the heat exchanger (e.g., the fins 8313) can also or alternatively include a braze layer formed on or applied to an outer surface, an inner sacrificial layer disposed under the braze layer or a portion of the braze layer, and a core disposed under the sacrificial layer. Alternatively or in addition, a core of the sheet of material used for forming the second portion of the heat exchanger (e.g., the fins 8313) can include an outer portion or layer of modified core material as described above. Moreover, each of the layers and sub layers of the sheets of material used for forming the second portion of the heat exchanger (e.g., the fins 8313) can be anodic to one or more underlying layers or sub layers. In some such embodiments, each of the layers and sub layers of the sheets of material 8333 used for forming the second portion of the heat exchanger (e.g., the fins 8313) is formed from a material or alloyed with a material such that there is a difference of at least about 30 millivolts between each adjacent layer of the second portion of the heat exchanger.

In some embodiments in which two or more portions of the heat exchanger are secured together, a first portion of the heat exchanger can be formed from a sheet of material having an outer portion or layer which is substantially anodic to an outer layer or portion of a second portion of the heat exchanger. For example, as shown in FIGS. 92-95, in some such embodiments, an outer portion or layer of the fin 8313 can be formed from a sheet of material 8333 which is anodic to a sheet of material 8317 used to form the heat exchanger tube 8310.

Alternatively or in addition, the outer portion or layer of the fin 8313 can be formed from a sheet of material 8333 which is anodic to a residual alpha-phase layer 8341 formed from the brazing material between the outer surfaces of the heat exchanger tube 8310 and the fin 8313. In some such embodiments, the residual alpha-phase layer 8341 is anodic to the sacrificial layer 8337 of the sheet of material 8317 forming the heat exchanger tube 8310.

In some embodiments of the present invention, first and second portions of a heat exchanger can be connected to opposite sides of a third portion of the heat exchanger. For example, in the illustrated embodiment of FIGS. 94 and 95, a heat exchanger tube 8310 having first and second outer surfaces X1, X2 is formed from a first sheet of material 8317. As shown in FIGS. 94 and 95, each side of the sheet of material 8317 can include a braze layer 8335 providing at least a portion of the outer surfaces X1, X2 of the first sheet of material 8317, an inner sacrificial layer or corrosion protection layer 8337 disposed under the braze layer 8335 or a portion of the braze layer 8335, and a core 8315 disposed between the sacrificial layers 8337. In some embodiments, the both outer sides of the core 8315 can include a sub layer 8339 of modified core material.

The inventors have found that corrosion protection for heat exchangers or portions of heat exchangers with relatively small wall thicknesses (e.g., wall thicknesses of less than about 0.20 mm (0.007874 in)) can be improved if the brazing time (i.e., the time when the heat exchanger or the portion of the heat exchanger being brazed passes through the brazing furnace) is reduced. The inventors have determined that a reduction of approximately 10% in brazing time shows desired results and can provide, among other advantages, good strength and corrosion resistance. Furthermore, results can be improved if the brazing time is further reduced by approximately one half.

More particularly, the inventors have found that increasing the brazing speed can reduce the diffusion of silicon from the braze layer 8335 into the underlying layers or sub layers of the sheet of material 8317. The diffusion of silicon is illustrated in FIGS. 93 and 95 with dashed arrows. The diffusion depth of the silicon can be less than about 50 μm (1.969 mil), or in some embodiments, can be significantly less. FIG. 96 graphically illustrates this relationship. The dashed curve in FIG. 96 represents the progression of the diffusion of the silicon, while the solid curve represents the progression of the diffusion in accordance with conventional materials and brazing techniques.

In some embodiments of the present invention, heat exchangers or portions of heat exchangers being brazed are placed on a conveyor or a similar transport device, which passes through different temperature zones of a CAB brazing furnace. In some such embodiments, the temperature of the brazing furnace can be in the range of approximately 577-610° C. (1070-1130° F.).

The optimal brazing time for a specific heat exchanger or for a specific portion of a heat exchanger depends, at least in part, upon the total mass of the heat exchanger or the portion of the heat exchanger being brazed, the temper condition of the sheets of material being brazed, the thickness of the sheets of material being brazed, and the composition of the sheets of material being brazed. For example, in some embodiments, the transport speed for brazing heat exchangers or portions of heat exchangers with wall thicknesses of 0.20 mm (0.007874 in) or more in a CAB brazing furnace is approximately 0.5-1.5 m/min (19.69-59.055 in/min).

Before brazing a heat exchanger or portion of a heat exchanger, the inventors have found that material samples having material properties substantially similar or identical to the heat exchanger or the portion of the heat exchanger being brazed can be used to experimentally determine an optimal temperature profile for the specific material of the heat exchanger or portion of the heat exchanger being brazed. The inventors have also found that by determining an optimal temperature profile, it is possible to increase the transport speed of the heat exchanger or the portion of the heat exchanger being brazed to about 1.5-4.0 m/min (4.92-13.12 ft/min), thereby reducing the brazing time.

In some embodiments, non-corrosive flux can be applied to the outer surface X1 of one or both aluminum sheets of material 8317, 8333 prior to brazing. In some embodiments, it may not be necessary to apply flux material to the outer surface X1 of one or both sheets of material 8317, 8333 to achieve high quality brazed connections. Moreover, in some embodiments, including embodiments in which flux material is not applied to the surfaces of the sheets of material 8317, 8333 prior to brazing, the inventors have determined that high quality internal brazing connections can be created in a controlled atmosphere by adding one or more alloys, such as, for example, magnesium and/or lithium to the sheets of material 8317, 8333.

Various features and advantages of the invention are set forth in the following claims. 

1-27. (canceled)
 28. A heat exchanger tube comprising: a first sheet of material and a second sheet of material together at least partially forming a tube body defining an interior space and having first and second opposing broad sides joined by first and second opposing narrow sides, the tube body having areas of overlapping material at the first and second narrow sides of the tube body in which portions of the first and second sheets of material overlap one another, the areas of overlapping material defining at least a majority of each of the first and second narrow sides of the tube body, at least one of the areas of overlapping material extending to and terminating at a location within the first broad side and between the first and second narrow sides of the tube body; and a third sheet of material forming an insert supported in the interior space of the tube body between the first sheet of material and the second sheet of material.
 29. The heat exchanger tube of claim 28, wherein: each of the first and second narrow sides has a concave shape facing the interior space of the tube body; and first and second portions of the insert are received within and reinforce the concave shape of the first and second narrow sides of the tube body, respectively.
 30. The heat exchanger tube of claim 28, wherein: each of the first and second narrow sides has a concave shape facing the interior space of the tube body; and first and second portions of the insert are nested within the concave shape of the first and second narrow sides of the tube body, respectively.
 31. The heat exchanger tube of claim 28, wherein a portion of the first sheet of material defines a recess, and wherein an end of the second sheet of material is at least partially nested in the recess such that an exterior surface of the first sheet of material adjacent the recess is substantially flush with an exterior surface of the second sheet of material in the recess.
 32. The heat exchanger tube of claim 31, wherein the recess extends into one of the first and second opposing broad sides of the tube body.
 33. The heat exchanger tube of claim 28, wherein a portion of the insert is received within the concave shape of one of the first and second narrow sides of the tube body, and is folded such that a first layer and a second layer of the insert are substantially parallel to at least one of the first and second broad sides of the tube body.
 34. The heat exchanger tube of claim 28, wherein the location is in a substantially planar portion of the first broad side of the tube body.
 35. The heat exchanger tube of claim 28, wherein the first sheet of material and the second sheet of material are substantially symmetrical.
 36. The heat exchanger tube of claim 28, wherein the first sheet of material and the second sheet of material are substantially identical.
 37. The heat exchanger tube of claim 28, wherein two of the areas of overlapping material extend to and terminate at respective locations within the first broad side and between the first and second narrow sides of the tube body.
 38. The heat exchanger tube of claim 28, wherein two of the areas of overlapping material extend to and terminate at respective locations within the first and second broad sides of the tube body, respectively.
 39. The heat exchanger tube of claim 28, wherein the thickness of each of the first sheet of material and the second sheet of material is no greater than about 0.15 mm.
 40. The heat exchanger tube of claim 28, wherein the thickness of each of the first sheet of material and the second sheet of material is no greater than about 0.10 mm.
 41. The heat exchanger tube of claim 28, wherein at least one of the first and second sheets of material has a first layer comprising an aluminum alloy, a second layer comprising an aluminum alloy having accumulations of an intermetallic compound including silicon, and a third layer comprising a metal material that is anodic with respect to the second layer and that is more resistant to the diffusion of silicon than the second layer, the second layer located between the first and third layers.
 42. A method of forming a heat exchanger tube, the method comprising: shaping a first sheet of material to form at least a portion of each of a first broad side, a first narrow side, and a second narrow side of a tube body, wherein the first and second narrow sides are opposite one another; shaping a second sheet of material to form at least a portion of each of a second broad side, the first narrow side, and the second narrow side of the tube body, wherein the first and second broad sides of the tube body are opposite one another and are joined by the first and second narrow sides of the tube body; shaping a third sheet of material to form an insert supported in an interior space of the tube body between the first sheet of material and the second sheet of material; and overlapping the first and second sheets of material at the first and second narrow sides to double the thickness of the tube body across at least a majority of the first and second narrow sides, each of the overlapped areas of the first and second sheets of material extending to and terminating at locations within at least one of the broad sides of the tube body between the first and second narrow sides of the tube body.
 43. The method of claim 42, further comprising receiving ends of the insert within concave portions of the first and second narrow sides of the tube body.
 44. The method of claim 43, further comprising nesting the ends of the insert within the concave portions of the first and second narrow sides of the tube body.
 45. The method of claim 42, wherein the thickness of the first and second sheets of material is no greater than about 0.15 mm.
 46. The method of claim 42, wherein the thickness of the first and second sheets of material is no greater than about 0.10 mm.
 47. The method of claim 42, wherein the first and second sheets of material each have a first layer comprising an aluminum alloy, a second layer comprising an aluminum alloy having accumulations of an intermetallic compound including silicon, and a third layer comprising a metal material that is anodic with respect to the second layer and that is more resistant to the diffusion of silicon than the second layer, the second layer located between the first and third layers.
 48. The method of claim 42, wherein shaping the first sheet of material includes shaping an edge of the first sheet of material to terminate in a substantially planar portion of the first broad side of the tube body.
 49. The method of claim 42, further comprising receiving an edge of the first sheet of material into a recess in an exterior of the second sheet of material.
 50. The method of claim 42, wherein the first and second sheets of material are shaped to be substantially identical.
 51. The method of claim 42, wherein the first and second sheets of material are shaped to be substantially symmetrical. 